Python Algorithm Interview

Important

Translated version from the Korean version into English with D3.js visualizations for the 88 main LeetCode problems, plus Appendix B solutions for 95 total algorithm problems.

🚀 Quick Start

👉 Open index.html to browse the interactive visualizations for problems 1-88.

★ Errata: https://www.onlybook.co.kr/entry/algorithm-interview-errata
★ Book Info: https://www.onlybook.co.kr/entry/algorithm-interview
★ YouTube: https://www.youtube.com/watch?v=fNyGHpSWhTA

Problem Solutions

#	Title	Difficulty	Chapter	Solution Code
1	Valid Palindrome	★	Ch6. String Manipulation	1-1.py 1-2.py 1-3.py 1-4.c
2	Reverse String	★	Ch6. String Manipulation	2-1.py 2-2.py
3	Reorder Data in Log Files	★	Ch6. String Manipulation	3-1.py
4	Most Common Word	★	Ch6. String Manipulation	4-1.py
5	Group Anagrams	★★	Ch6. String Manipulation	5-1.py
6	Longest Palindromic Substring	★★	Ch6. String Manipulation	6-1.py
7	Two Sum	★	Ch7. Arrays	7-1.py 7-2.py 7-3.py 7-4.py 7-5.py 7-6.go
8	Trapping Rain Water	★★★	Ch7. Arrays	8-1.py 8-2.py
9	3Sum	★★	Ch7. Arrays	9-1.py 9-2.py
10	Array Partition I	★	Ch7. Arrays	10-1.py 10-2.py 10-3.py
11	Product of Array Except Self	★★	Ch7. Arrays	11-1.py
12	Best Time to Buy and Sell Stock	★	Ch7. Arrays	12-1.py 12-2.py
13	Palindrome Linked List	★	Ch8. Linked Lists	13-1.py 13-2.py 13-3.go 13-4.py
14	Merge Two Sorted Lists	★	Ch8. Linked Lists	14-1.py
15	Reverse Linked List	★	Ch8. Linked Lists	15-1.py 15-2.py
16	Add Two Numbers	★★	Ch8. Linked Lists	16-1.py 16-2.py
17	Swap Nodes in Pairs	★★	Ch8. Linked Lists	17-1.py 17-2.py 17-3.py
18	Odd Even Linked List	★★	Ch8. Linked Lists	18-1.py
19	Reverse Linked List II	★★	Ch8. Linked Lists	19-1.py
20	Valid Parentheses	★	Ch9. Stack, Queue	20-1.py
21	Remove Duplicate Letters	★★★	Ch9. Stack, Queue	21-1.py 21-2.py
22	Daily Temperatures	★★	Ch9. Stack, Queue	22-1.py
23	Implement Stack using Queues	★	Ch9. Stack, Queue	23-1.py
24	Implement Queue using Stacks	★	Ch9. Stack, Queue	24-1.py
25	Design Circular Queue	★★	Ch9. Stack, Queue	25-1.py
26	Design Circular Deque	★★	Ch10. Deque, Priority Queue	26-1.py
27	Merge k Sorted Lists	★	Ch10. Deque, Priority Queue	27-1.py
28	Design HashMap	★	Ch11. Hash Table	28-1.py
29	Jewels and Stones	★	Ch11. Hash Table	29-1.py 29-2.py 29-3.py 29-4.py
30	Longest Substring Without Repeating Characters	★★	Ch11. Hash Table	30-1.py
31	Top K Frequent Elements	★★	Ch11. Hash Table	31-1.py 31-2.py
32	Number of Islands	★★	Ch12. Graph	32-1.py
33	Letter Combinations of a Phone Number	★★	Ch12. Graph	33-1.py
34	Permutations	★★	Ch12. Graph	34-1.py 34-2.py
35	Combinations	★★	Ch12. Graph	35-1.py 35-2.py
36	Combination Sum	★★	Ch12. Graph	36-1.py
37	Subsets	★★	Ch12. Graph	37-1.py
38	Reconstruct Itinerary	★★	Ch12. Graph	38-1.py 38-2.py 38-3.py
39	Course Schedule	★★	Ch12. Graph	39-1.py 39-2.py
40	Network Delay Time	★★	Ch13. Shortest Path	40-1.py
41	Cheapest Flights Within K Stops	★★	Ch13. Shortest Path	41-1.py
42	Maximum Depth of Binary Tree	★	Ch14. Tree	42-1.py
43	Diameter of Binary Tree	★	Ch14. Tree	43-1.py
44	Longest Univalue Path	★	Ch14. Tree	44-1.py
45	Invert Binary Tree	★	Ch14. Tree	45-1.py 45-2.py 45-3.py 45-4.py
46	Merge Two Binary Trees	★	Ch14. Tree	46-1.py
47	Serialize and Deserialize Binary Tree	★★★	Ch14. Tree	47-1.py
48	Balanced Binary Tree	★	Ch14. Tree	48-1.py
49	Minimum Height Trees	★★	Ch14. Tree	49-1.py
50	Convert Sorted Array to Binary Search Tree	★	Ch14. Tree	50-1.py
51	Binary Search Tree to Greater Sum Tree	★★	Ch14. Tree	51-1.py
52	Range Sum of BST	★	Ch14. Tree	52-1.py 52-2.py 52-3.py 52-4.py
53	Minimum Distance Between BST Nodes	★	Ch14. Tree	53-1.py 53-2.py
54	Construct Binary Tree from Preorder and Inorder Traversal	★★	Ch14. Tree	54-1.py
55	Kth Largest Element in an Array	★★	Ch15. Heap	55-1.py 55-2.py 55-3.py 55-4.py
56	Implement Trie (Prefix Tree)	★★	Ch16. Trie	56-1.py
57	Palindrome Pairs	★★★	Ch16. Trie	57-1.py 57-2.py
58	Sort List	★★	Ch17. Sorting	58-1.py 58-3.py
59	Merge Intervals	★★	Ch17. Sorting	59-1.py
60	Insertion Sort List	★★	Ch17. Sorting	60-1.py 60-2.py
61	Largest Number	★★	Ch17. Sorting	61-1.py
62	Valid Anagram	★	Ch17. Sorting	62-1.py
63	Sort Colors	★★	Ch17. Sorting	63-1.py
64	K Closest Points to Origin	★★	Ch17. Sorting	64-1.py
65	Binary Search	★	Ch18. Binary Search	65-1.py 65-2.py 65-3.py 65-4.py
66	Search in Rotated Sorted Array	★★	Ch18. Binary Search	66-1.py
67	Intersection of Two Arrays	★	Ch18. Binary Search	67-1.py 67-2.py 67-3.py
68	Two Sum II - Input Array Is Sorted	★	Ch18. Binary Search	68-1.py 68-2.py 68-3.py 68-4.py 68-5.py
69	Search a 2D Matrix II	★★	Ch18. Binary Search	69-1.py 69-2.py
70	Single Number	★	Ch19. Bit Manipulation	70-1.py
71	Hamming Distance	★	Ch19. Bit Manipulation	71-1.py
72	Sum of Two Integers	★★★	Ch19. Bit Manipulation	72-1.py 72-2.py
73	UTF-8 Validation	★★	Ch19. Bit Manipulation	73-1.py
74	Number of 1 Bits	★	Ch19. Bit Manipulation	74-1.py 74-2.py
75	Sliding Window Maximum	★★★	Ch20. Sliding Window	75-1.py 75-2.py
76	Minimum Window Substring	★★★	Ch20. Sliding Window	76-1.py 76-2.py 76-3.py
77	Longest Repeating Character Replacement	★★	Ch20. Sliding Window	77-1.py
78	Best Time to Buy and Sell Stock II	★	Ch21. Greedy Algorithm	78-1.py 78-2.py
79	Queue Reconstruction by Height	★★	Ch21. Greedy Algorithm	79-1.py
80	Task Scheduler	★★	Ch21. Greedy Algorithm	80-1.py
81	Gas Station	★★	Ch21. Greedy Algorithm	81-1.py 81-2.py
82	Assign Cookies	★	Ch21. Greedy Algorithm	82-1.py 82-2.py
83	Majority Element	★	Ch22. Divide and Conquer	83-1.py 83-2.py 83-3.py 83-4.py
84	Different Ways to Add Parentheses	★★	Ch22. Divide and Conquer	84-1.py
85	Fibonacci Number	★	Ch23. Dynamic Programming	85-1.py 85-2.py 85-3.py 85-4.py
86	Maximum Subarray	★	Ch23. Dynamic Programming	86-1.py 86-2.py
87	Climbing Stairs	★	Ch23. Dynamic Programming	87-1.py 87-2.py
88	House Robber	★	Ch23. Dynamic Programming	88-1.py 88-2.py
89 (Problem 1)	Secret Map	★	Appendix B. Kakao Blind Recruitment Problems	1.py
90 (Problem 2)	Dart Game	★	Appendix B. Kakao Blind Recruitment Problems	2.py
91 (Problem 3)	Cache	★	Appendix B. Kakao Blind Recruitment Problems	3.py
92 (Problem 4)	Shuttle Bus	★★	Appendix B. Kakao Blind Recruitment Problems	4.py
93 (Problem 5)	News Clustering	★★	Appendix B. Kakao Blind Recruitment Problems	5.py
94 (Problem 6)	Friends 4 Block	★★★	Appendix B. Kakao Blind Recruitment Problems	6.py
95 (Problem 7)	Chuseok Traffic	★★★	Appendix B. Kakao Blind Recruitment Problems	7.py

Additional Code (miscellaneous)

• Ch4 Performance Comparison
• Ch9 Stack
• Ch11 Birthday Problem
• Ch12 Graph Traversals
• Ch14 Tree Traversals
• Ch15 Binary Heap
• Ch17 Bubble Sort
• Ch17 Quick Sort
• Ch21 Fractional Knapsack Problem
• Ch23 0-1 Knapsack Problem

LeetCode Updates and More Efficient Solutions

• Problem 7: Test cases were removed, resulting in different execution times. #62
• Problem 25: For a more efficient solution, see #105.
• Problem 33: For a more efficient solution, see #91.
• Problem 35: For a more efficient solution, see #111.
• Problem 36: For a more efficient solution, see #112.
• Problem 41: Due to test case changes, the solution now times out. #104
• Problem 47: Due to evaluation function changes, comment out the TreeNode declaration before running. #97
• Problem 75: Additional test cases were added, solution no longer passes. For new solution, see #67.