A personal history of leetcode

✅ 46. Permutations
✅ 70. Climbing Stairs
✅ 62. Unique Paths

✅ 54. Spiral Matrix
✅ 56. Merge Intervals
✅ 57. Insert Interval 【hard】
✅ 59. Spiral Matrix II

✅ 🌟 45. Jump Game II 【greedy】
✅ 48. Rotate Image
✅ 49. Group Anagrams
✅ 50. Pow(x, n)
✅ 53. Maximum Subarray
✅ 55. Jump Game

✅ 41. First Missing Positive

water problems - dp
✅ 🌟 42. Trapping Rain Water
✅ 238. Product of Array Except Self
11
❎ 407

✅ 35. Search Insert Position
✅ 36. Valid Sudoku
✅ 37. Sudoku Solver
✅ 38. Count and Say

✅ 131. Palindrome Partitioning
✅ 40. Combination Sum II
✅ 31. Next Permutation
✅ 33. Search in Rotated Sorted Array
✅ 34. Find First and Last Position of Element in Sorted Array

Permutation
✅ 31. Next Permutation
✅ 46. Permutations
✅ 78. Subsets
✅ 90. Subsets II

✅ 200. Number of Islands

✅ 28. Implement strStr()

拓扑排序
✅ 207. Course Schedule
✅ 210. Course Schedule II
❎ 329. Longest Increasing Path in a Matrix

❎ 29， 23

括号题
✅ 20. Valid Parentheses
✅ 22. Generate Parentheses
✅ 🌟 856. Score of Parentheses
✅ 🌟 241. Different Ways to Add Parentheses

✅ 26. Remove Duplicates from Sorted Array
✅ 27. Remove Element

❎ 🌟 301

复习6题，新题2题
✅ 15. 3Sum
✅ 18. 4Sum
✅ 20. Valid Parentheses

复习7题，新题3题
✅ 15. 3Sum
✅ 12. Integer to Roman
✅ 13. Roman to Integer
✅ 8. String to Integer (atoi)
✅ 17. Letter Combinations of a Phone Number
✅ 18. 4Sum

❎ 🌟 10

复习6题，新题2题
✅ tree - dfs, bfs, construct binary search tree
✅ 11. Container With Most Water

========================================================

670 46 47 36 .
284, 211, 208, 212, 999, 399, 481, 498, 500,
451, 452, 453, 454, 455, 456, 457, 458, 461,
513, 515, 516, 518, 520, 521, 522, 523, 524,

=========================================================

277, 220, 45, 121, 122, 123, 309, 11

29, 165, 8, 50, 365, 204

124, 250, 366, 337, 235, 173, 297， 285， 270， 272， 99

369,

• array: 220,
• word pattern match 205, 290
• linked list cycle 141, 142
• slow and quick pointers 26
• recursive / iterative (tree) 144, 110
• linked list: 24, 92, 160, 143， 148, 25, 23
• binary search 33, 153, 162
• other: 406,

287 Find the Duplicate Number
56. Merge Intervals

55.Jump Game

229.Majority Element II 【摩尔枚举：n个数取k个值】
274. H-Index
275. H-Index II
217. Contains Duplicate
219. Contains Duplicate II [star]

299.Bulls and Cows
134. Gas Station
118. Pascal's Triangle
119. Pascal's Triangle II
169. Majority Element

27, 26, 80, 189,
41. First Missing Positive

39.Combination Sum
40. Combination Sum II
48. Rotate Image
54. Spiral Matrix
59. Spiral Matrix II

14.Longest Common Prefix
15. 3Sum
16. 3Sum Closest
18. 4Sum
22. Generate Parentheses

16.3Sum Closest

832.Flipping an Image
12. Integer to Roman

647.Palindromic Substrings
17. Letter Combinations of a Phone Number

78.Subsets
90. Subsets II
338. Counting Bits
406. Queue Reconstruction by Height

226.Invert Binary Tree
257. Binary Tree Paths
112. Path Sum

100.Same Tree
101. Symmetric Tree

147.Insertion Sort List
278. First Bad Version
35. Search Insert Position
33. Search in Rotated Sorted Array
81. Search in Rotated Sorted Array II
153. Find Minimum in Rotated Sorted Array
162. Find Peak Element
374. Guess Number Higher or Lower
34. Find First and Last Position of Element in Sorted Array
349. Intersection of Two Arrays

61.Rotate List
86. Partition List

142.Linked List Cycle II [fast and slow pointers]
148. Sort List 【merge sort】

203.Remove Linked List Elements
82. Remove Duplicates from Sorted List II
2. Add Two Numbers
21. Merge Two Sorted Lists
234. Palindrome Linked List

92.Reverse Linked List II .
237. Delete Node in a Linked List . ......
19. Remove Nth Node From End of List
83. Remove Duplicates from Sorted List 160. Intersection of Two Linked Lists

206.Reverse Linked List .
141. Linked List Cycle .
24. Swap Nodes in Pairs .
328. Odd Even Linked List

109.Convert Sorted List to Binary Search Tree .
230. Kth Smallest Element in a BST .
98. Validate Binary Search Tree .
125. Valid Palindrome .
429. N-ary Tree Level Order Traversal

107.Binary Tree Level Order Traversal II .
103. Binary Tree Zigzag Level Order Traversal .
199. Binary Tree Right Side View .
226. Invert Binary Tree .
404. Sum of Left Leaves .
235. Lowest Common Ancestor of a Binary Search Tree .
236. Lowest Common Ancestor of a Binary Tree (same as 235...) .
108. Convert Sorted Array to Binary Search Tree .

110.Balanced Binary Tree (balanced binary tree) 【two recursion】

257.Binary Tree Paths
112. Path Sum
113. Path Sum II
129. Sum Root to Leaf Numbers
111. Minimum Depth of Binary Tree
104. Maximum Depth of Binary Tree

145.Binary Tree Postorder Traversal [review] postorder: preorder(root->right->left) then reverse
102. Binary Tree Level Order Traversal
100. Same Tree
101. Symmetric Tree

144.Binary Tree Preorder Traversal [review] [preorder]
z94. Binary Tree Inorder Traversal [inorder]
145. Binary Tree Postorder Traversal [postorder]

200.Number of Islands
66.Plus One
144.Binary Tree Preorder Traversal

7.Reverse Integer

189.Rotate Array
258.Add Digits (simple recursion)
231.Power of Two

27.Remove Element
26. Remove Duplicates from Sorted Array
80. Remove Duplicates from Sorted Array II

387.First Unique Character in a String
383. Ransom Note
345. Reverse Vowels of a String

242.Valid Anagram
49. Group Anagrams
168. Excel Sheet Column Title
171. Excel Sheet Column Number

13.Roman to Integer
67. Add Binary
344. Reverse String
151. Reverse Words in a String
345. Reverse Vowels of a String

28.Implement strStr()
58. Length of Last Word

169.Majority Element
229. Majority Element II
274. H-Index
275. H-Index II

81.Search in Rotated Sorted Array II
33. Search in Rotated Sorted Array

771.Jewels and Stones [hash table]
3.
890. Find and Replace Pattern

11.Container With Most Water [medium star]

172.factorial-trailing-zeroes [tricky issue]
169. Majority Element

121.Best Time to Buy and Sell Stock [review]
136. single-number 异或^：XOR 相同为0，不同为1，0与任何数^为0
167. two-sum-ii-input-array-is-sorted

121. Best Time to Buy and Sell Stock

20.valid parentheses [review]
26. remove duplicates in a sorted array

20. valid parentheses