Added new solutions

Michael Ho · Michael Ho · commit 9aabad5537a0 · 2018-09-18T22:42:58.000-04:00
diff --git a/Easy/0027-RemoveElement.playground/Contents.swift b/Easy/0027-RemoveElement.playground/Contents.swift
@@ -0,0 +1,16 @@
+// LeetCode: https://leetcode.com/problems/remove-element/description/
+
+class Solution {
+    func removeElement(_ nums: inout [Int], _ val: Int) -> Int {
+        nums = nums.filter { $0 != val }
+        return nums.count
+    }
+}
+
+let solution = Solution()
+var arr1 = [3,2,2,3]
+print("\(solution.removeElement(&arr1, 3))") // 2
+print(arr1)
+var arr2 = [0,1,2,2,3,0,4,2]
+print("\(solution.removeElement(&arr2, 2))") // 5
+print(arr2)
diff --git a/Easy/0027-RemoveElement.playground/contents.xcplayground b/Easy/0027-RemoveElement.playground/contents.xcplayground
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>
diff --git a/Easy/0028-ImplementstrStr().playground/Contents.swift b/Easy/0028-ImplementstrStr().playground/Contents.swift
@@ -0,0 +1,26 @@
+// LeetCode: https://leetcode.com/problems/implement-strstr/description/
+
+class Solution {
+    func strStr(_ haystack: String, _ needle: String) -> Int {
+        var index = -1
+        guard needle.count > 0 else {
+            return 0
+        }
+        var nArr = Array(needle)
+        var hArr = Array(haystack)
+        for (idx, c) in hArr.enumerated() {
+            if c == nArr[0], idx + (nArr.count) <= hArr.count, String(hArr[idx..<idx + (nArr.count)]) == needle {
+                index = idx
+                break
+            }
+        }
+        return index
+    }
+}
+
+let solution = Solution()
+print(solution.strStr("hello", "ll")) // 2
+print(solution.strStr("aaa", "aa")) // 0
+print(solution.strStr("aaa", "a")) // 0
+print(solution.strStr("", "")) // 0
+print(solution.strStr("a", "a")) // 0
diff --git a/Easy/0028-ImplementstrStr().playground/contents.xcplayground b/Easy/0028-ImplementstrStr().playground/contents.xcplayground
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='macos'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>
diff --git a/Easy/0035-SearchInsertPosition.playground/Contents.swift b/Easy/0035-SearchInsertPosition.playground/Contents.swift
@@ -0,0 +1,21 @@
+// LeetCode: https://leetcode.com/problems/search-insert-position/description/
+
+class Solution {
+    func searchInsert(_ nums: [Int], _ target: Int) -> Int {
+        var output = 0
+        for i in 0..<nums.count {
+            if target > nums[i] {
+                output = i + 1
+            } else if target == nums[i] {
+                output = i
+            }
+        }
+        return output
+    }
+}
+
+let solution = Solution()
+print(solution.searchInsert([1,3,5,6], 5)) // 2
+print(solution.searchInsert([1,3,5,6], 2)) // 1
+print(solution.searchInsert([1,3,5,6], 7)) // 4
+print(solution.searchInsert([1,3,5,6], 0)) // 0
diff --git a/Easy/0035-SearchInsertPosition.playground/contents.xcplayground b/Easy/0035-SearchInsertPosition.playground/contents.xcplayground
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='macos'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>
diff --git a/Easy/0053-MaximumSubarray.playground/Contents.swift b/Easy/0053-MaximumSubarray.playground/Contents.swift
@@ -0,0 +1,22 @@
+// LeetCode: https://leetcode.com/problems/maximum-subarray/description/
+
+class Solution {
+    func maxSubArray(_ nums: [Int]) -> Int {
+        var max = nums[0]
+        for i in 0..<nums.count {
+            var current = nums[i]
+            max = current > max ? current : max
+            var index = i + 1
+            while index < nums.count {
+                current += nums[index]
+                max = current > max ? current : max
+                index += 1
+            }
+        }
+        return max
+    }
+}
+
+let solution = Solution()
+print(solution.maxSubArray([-2,1,-3,4,-1,2,1,-5,4])) // 6
+print(solution.maxSubArray([-2,1])) // 1
diff --git a/Easy/0053-MaximumSubarray.playground/contents.xcplayground b/Easy/0053-MaximumSubarray.playground/contents.xcplayground
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='macos'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>
diff --git a/Medium/0011-ContainerWithMostWater.playground/Contents.swift b/Medium/0011-ContainerWithMostWater.playground/Contents.swift
@@ -0,0 +1,25 @@
+// LeetCode: https://leetcode.com/problems/container-with-most-water/description/
+
+class Solution {
+    func maxArea(_ height: [Int]) -> Int {
+        var area = 0
+        var start = 0
+        var end = height.count - 1
+        while start < end {
+            let areaH = min(height[start], height[end])
+            let width = end - start
+            if areaH * width > area {
+                area = areaH * width
+            }
+            if height[start] < height[end] {
+                start += 1
+            } else {
+                end -= 1
+            }
+        }
+        return area
+    }
+}
+
+let solution = Solution()
+print("\(solution.maxArea([1,8,6,2,5,4,8,3,7]))") // 49
diff --git a/Medium/0011-ContainerWithMostWater.playground/contents.xcplayground b/Medium/0011-ContainerWithMostWater.playground/contents.xcplayground
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='macos'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>
diff --git a/Medium/0015-3Sum.playground/Contents.swift b/Medium/0015-3Sum.playground/Contents.swift
@@ -6,33 +6,31 @@ class Solution {
         guard nums.count >= 3 else {
             return []
         }
-        nums.sorted()
-        var idxArr: [[Int]] = []
-        var pair: [[Int]] = []
-        var num1: [Int] = []
-        for idx1 in 0..<nums.count {
-            if num1.contains(nums[idx1]) {
-                break
+        let sort = nums.sorted()
+        var output: [[Int]] = []
+        for i in 0..<sort.count - 2 {
+            if i > 0, sort[i] == sort[i-1] {
+                continue
             }
-            num1.append(nums[idx1])
-            for idx2 in idx1+1..<nums.count {
-                if pair.contains([nums[idx1], nums[idx2]].sorted()) {
-                    continue
+            var start = i + 1
+            var end = sort.count - 1
+            while start < end {
+                if sort[i] + sort[start] + sort[end] == 0 {
+                    output.append([sort[i], sort[start], sort[end]])
+                    start += 1
+                    end -= 1
+                } else if sort[i] + sort[start] + sort[end] < 0 {
+                    start += 1
                 } else {
-                    pair.append([nums[idx1], nums[idx2]].sorted())
-                    idxArr.append([idx1, idx2])
+                    end -= 1
                 }
-            }
-        }
-        var output: [[Int]] = []
-        for i in 0..<nums.count {
-            for pair in idxArr {
-                if i == pair[0] || i == pair[1] {
+                if start - 1 >= 0 && sort[start] == sort[start - 1] {
+                    start += 1
                     continue
                 }
-                
-                if nums[i] + nums[pair[0]] + nums[pair[1]] == 0, !output.contains([nums[i], nums[pair[0]], nums[pair[1]]].sorted()) {
-                    output.append([nums[i], nums[pair[0]], nums[pair[1]]].sorted())
+                if end + 1 < sort.count && sort[end] == sort[end + 1] {
+                    end -= 1
+                    continue
                 }
             }
         }
@@ -68,6 +66,15 @@ print("---------------------------------")
     [-1, 0, 1]
  ]
  */
+print("\(solution.threeSum([-2,0,1,1,2]))")
+/**
+ The solution set is:
+ [
+    [-2,0,2],
+    [-2,1,1]
+ ]
+ */
+print("\(solution.threeSum([1,1,1]))") // [[]]
 let longArray1 = [-2,10,-14,11,5,-4,2,0,-10,-10,5,7,-11,10,-2,-5,2,12,-5,14,-11,-15,-5,12,0,13,8,7,10,6,-9,-15,1,14,11,-9,-13,-10,6,-8,-5,-11,6,-9,14,11,-7,-6,8,3,-7,5,-5,3,2,10,-6,-12,3,11,1,1,12,10,-8,0,8,-5,6,-8,-6,8,-12,-14,7,9,12,-15,-12,-2,-4,-4,-12,6,7,-3,-6,-14,-8,4,4,9,-10,-7,-4,-3,1,11,-1,-8,-12,9,7,-9,10,-1,-14,-1,-8,11,12,-5,-7]
 print(longArray1.count)
 print("\(solution.threeSum(longArray1))") // Test time limit
@@ -76,11 +83,3 @@ let longArray2 = [12,-14,-5,12,-2,9,0,9,-3,-3,-14,-6,-4,13,-11,-8,0,5,-7,-6,-10,
 print(longArray2.count)
 print("\(solution.threeSum(longArray2))") // Test time limit
 print("---------------------------------")
-print("\(solution.threeSum([-2,0,1,1,2]))")
-/**
- The solution set is:
- [
-    [-2,0,2],
-    [-2,1,1]
- ]
-*/
diff --git a/Medium/0018-4Sum.playground/Contents.swift b/Medium/0018-4Sum.playground/Contents.swift
@@ -0,0 +1,73 @@
+// LeetCode: https://leetcode.com/problems/4sum/description/
+// Difficulty: Medium
+// O(n^3) is acceptable
+
+class Solution {
+    func fourSum(_ nums: [Int], _ target: Int) -> [[Int]] {
+        var output: [[Int]] = []
+        var sortedNums = nums.sorted()
+        for idx1 in 0..<sortedNums.count {
+            for idx2 in (idx1+1)..<sortedNums.count {
+                var start = idx2 + 1
+                var end = sortedNums.count - 1
+                let comp = target - sortedNums[idx1] - sortedNums[idx2]
+                while start < end {
+                    if comp == sortedNums[start] + sortedNums[end], !output.contains([sortedNums[idx1], sortedNums[idx2], sortedNums[start], sortedNums[end]]) {
+                        output.append([sortedNums[idx1], sortedNums[idx2], sortedNums[start], sortedNums[end]])
+                        if end - start == 2 {
+                            start += 1
+                            continue
+                        }
+                        start += 1
+                        end -= 1
+                    } else if comp > sortedNums[start] + sortedNums[end] {
+                        start += 1
+                    } else {
+                        end -= 1
+                    }
+                }
+            }
+        }
+        return output
+    }
+}
+
+let solution = Solution()
+print("\(solution.fourSum([1, 0, -1, 0, -2, 2], 0))")
+/**
+ // Sorted: [-2, -1, 0, 0, 1, 2]
+ [
+ [-1,  0, 0, 1],
+ [-2, -1, 1, 2],
+ [-2,  0, 0, 2]
+ ]
+ */
+print("\(solution.fourSum([-1, 0, -5, -2, -2, -4, 0, 1, -2], -9))")
+/**
+ // Sorted: [-5, -4, -2, -2, -2, -1, 0, 0, 1]
+ [
+ [-5,-4,-1,1],
+ [-5,-4,0,0],
+ [-5,-2,-2,0],
+ [-4,-2,-2,-1]
+ ]
+ */
+print("\(solution.fourSum([0, 0, 0, 0], 0))")
+/**
+ [
+ [0, 0, 0, 0]
+ ]
+ */
+print("\(solution.fourSum([-3,-2,-1,0,0,1,2,3], 0))")
+/**
+ [
+ [-3, -2, 2, 3],
+ [-3, -1, 1, 3],
+ [-3, 0, 0, 3],
+ [-3, 0, 1, 2],
+ [-2, -1, 0, 3],
+ [-2, -1, 1, 2],
+ [-2, 0, 0, 2],
+ [-1, 0, 0, 1]
+ ]
+ */
diff --git a/Medium/0018-4Sum.playground/contents.xcplayground b/Medium/0018-4Sum.playground/contents.xcplayground
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='macos'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>
diff --git a/Medium/0029-DivideTwoIntegers.playground/Contents.swift b/Medium/0029-DivideTwoIntegers.playground/Contents.swift
@@ -0,0 +1,13 @@
+// LeetCode: https://leetcode.com/problems/divide-two-integers/description/
+
+class Solution {
+    func divide(_ dividend: Int, _ divisor: Int) -> Int {
+        var output = dividend / divisor
+        output = output > Int32.max ? Int(Int32.max) : output
+        output = output < Int32.min ? Int(Int32.min) : output
+        return output
+    }
+}
+
+let solution = Solution()
+print(solution.divide(-2147483648, -1)) // 2147483647
diff --git a/Medium/0029-DivideTwoIntegers.playground/contents.xcplayground b/Medium/0029-DivideTwoIntegers.playground/contents.xcplayground
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='macos'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>
diff --git a/Medium/0039-CombinationSum.playground/Contents.swift b/Medium/0039-CombinationSum.playground/Contents.swift
@@ -0,0 +1,47 @@
+// LeetCode: https://leetcode.com/problems/combination-sum/description/
+
+class Solution {
+    func combinationSum(_ candidates: [Int], _ target: Int) -> [[Int]] {
+        guard target > 0 else {
+            return []
+        }
+        var output: [[Int]] = []
+        for start in candidates {
+            var newSeq: [Int] = [start]
+            combinationSum(&output, &newSeq, candidates, target - start)
+        }
+        return output
+    }
+    
+    func combinationSum(_ output: inout [[Int]], _ sequance: inout [Int], _ candidates: [Int], _ target: Int) {
+        if target == 0, !output.contains(sequance.sorted()) {
+            output.append(sequance.sorted())
+            return
+        }
+        guard target > 0 else { return }
+        for i in candidates {
+            var temp = sequance
+            temp.append(i)
+            combinationSum(&output, &temp, candidates, target - i)
+        }
+    }
+}
+
+let solution = Solution()
+print(solution.combinationSum([2,3,6,7], 7))
+/**
+ The output should be:
+ [
+    [2,2,3]
+    [7]
+ ]
+ */
+print(solution.combinationSum([2,3,5], 8))
+/**
+ The output should be:
+ [
+    [2,2,2,2]
+    [2,3,3]
+    [3,5]
+ ]
+ */
diff --git a/Medium/0039-CombinationSum.playground/contents.xcplayground b/Medium/0039-CombinationSum.playground/contents.xcplayground
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='macos'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>
diff --git a/Medium/0040-CombinationSumII.playground/Contents.swift b/Medium/0040-CombinationSumII.playground/Contents.swift
diff --git a/Medium/0040-CombinationSumII.playground/contents.xcplayground b/Medium/0040-CombinationSumII.playground/contents.xcplayground
