随着做过的题越来越多，我觉得我需要一个目录来让我飞快的找到题目。
| 题目名称 | 难易程度 | 可考虑的解法 |
| 133. Clone Graph | Medium | bfs, map to store new node and old node |
| 973. K Closest Points to Origin | Medium | priority_queue, min heap |
| 238. Product of Array Except Self | Medium | multiply numbers from one side to another side |
| 953. Verifying an Alien Dictionary | Easy | HashMap store the index(which is order) |
| 9. Palindrome Number | Easy | Using properties of panlidrome |
| 3. Longest Substring Without Repeating Characters | Medium | Sliding window, array enumation |
| 399. Evaluate Division | Medium | directed graph |
| 712. Minimum ASCII Delete Sum for Two Strings | Medium | DP |
| 845. Longest Mountain in Array | Medium | Discuss in case |
| 815. Bus Routes | Hard | BFS |
| 204. Count Primes | Easy | check every number read detals |
| 190. Reverse Bits | Easy | Bit operation |
| 154. Find Minimum in Rotated Sorted Array II | Hard | Binary Search |
| 165. Compare Version Numbers | Medium | compare every sigle number |
| 187. Repeated DNA Sequences | Medium | using map |
| 698. Partition to K Equal Sum Subsets | Medium | DFS / DP |
| 445. Add Two Numbers II | Medium | Using Stack |
| 582. Kill Process | Medium | using queue to help |
| 74. Search a 2D Matrix | Medium | Binary Search |
| 129. Sum Root to Leaf Numbers | Medium | Recursion |
| 199. Binary Tree Right Side View | Medium | Layer traverse |
| 831. Masking Personal Information | Medium | Check every situations |
| 516. Longest Palindromic Subsequence | Medium | Dynamic Programming |
| 251. Flatten 2D Vector | Medium | using iterators |
| 140. Word Break II | hard | memorized searching |
| 296. Best Meeting Point | hard | Hamilton distance read details |
| 450. Delete Node in a BST | Medium | recursion read details |
| 290. Word Pattern | Easy | Using hashmap |
| 266. Palindrome Permutation | Easy | counting the appearance times of characteristics |
| 186. Reverse Words in a String II | Medium | using stack |
| 648. Replace Words | Medium | HashMap |
| 203. Remove Linked List Elements | Easy | check every nodes and recorde previous node |
| 442. Find All Duplicates in an Array | Medium | read details(assign each number to its position |
| 807. Max Increase to Keep City Skyline | Medium | find column maximum and row maximum |
| 433. Minimum Genetic Mutation | Medium | using bfs to test every possible mutation |
| 205. Isomorphic Strings | Easy | using hash-map to store last position |
| 457. Circular Array Loop | Medium | using fast and slow pointers |
| 735. Asteroid Collision | Medium | using vector to store the alive asteroid |
| 722. Remove Comments | Medium | check every character one by one |
| 298. Binary Tree Longest Consecutive Sequence | Medium | recursion |
| 117. Populating Next Right Pointers in Each Node II | Medium | nested loop with pointers (read details) |
| 116. Populating Next Right Pointers in Each Node | Medium | layer traverse by queue |
| 163. Missing Ranges | Medium | traverse the array |
| 727. Minimum Window Subsequence | Hard | DP |
| 336. Palindrome Pairs | Hard | Hash Map |
| 642. Design Search Autocomplete System | Hard | Trie tree with priority queue |
| 65. Valid Number | Hard | DFA |
| 139. Word Break | Medium | DP |
| 489. Robot Room Cleaner | Hard | DFS and store relative position to avoid infinite loop |
| 745. Prefix and Suffix Search | Hard | Trie tree |
| 56. Merge Intervals | Medium | sort and merge |
| 67. Add Binary | Easy | String operation |
| 256. Paint House | Easy | DP |
| 265. Paint House II | Hard | DP |
| 275. H-Index II | Medium | Binary search |
| 410. Split Array Largest Sum | Hard | Greedy and Binary search |
| 88. Merge Sorted Array | Easy | fill spaces back to front |
| 801. Minimum Swaps To Make Sequences Increasing |
Medium | DP |
| 764. Largest Plus Sign | Medium | traverse the matrix |
| 865. Smallest Subtree with all the Deepest Nodes | Medium | post-order traverse by recursion |
| 426. Convert Binary Search Tree to Sorted Doubly Linked List | Medium | In-order traverse by iteration |
| 334. Increasing Triplet Subsequence | Medium | read details |
| 639. Decode Ways II | Hard | watch out cornner cases |
| 784. Letter Case Permutation | Easy | change to the same case and then change |
| 68. Text Justification | Hard | read details |
| 109. Convert Sorted List to Binary Search Tree | Meidum | Divide and Conquer |
| 173. Binary Search Tree Iterator | Medium | use stack to help |
| 543. Diameter of Binary Tree | Easy | recursion; read question carefully!! |
| 20. Valid Parentheses | Easy | using stack |
| 269. Alien Dictionary | Hard | Topological sort |
| 554. Brick Wall | Medium | Analyze the questions first! used Map |
| 721. Accounts Merge | Medium | Union Find |
| 824. Goat Latin | Easy | Using stringstream and apply the rule |
| 689. Maximum Sum of 3 Non-Overlapping Subarrays | Hard | Divide it into 3 parts and DP |
| 283. Move Zeroes | Easy | 2 pointers |
| 282. Expression Add Operators | Hard | DFS and consider the priority |
| 158. Read N Characters Given Read4 II - Call multiple times | Hard | read Details |
| 210. Course Schedule II | Medium | topological sorting |
| 286. Walls and Gates | Medium | BFS |
| 750. Number Of Corner Rectangles | Medium | taverse with pruning |
| 274. H-Index | Medium | understanding the questions first! |
| 636. Exclusive Time of Functions | Medium | using stack and pointers |
| 477. Total Hamming Distance | Medium | finding the rule in the changing |
| 380. Insert Delete GetRandom O(1) | Medium | map and array, the point is O(1) |
| 825. Friends Of Appropriate Ages | Medium | analysis given inequation |
| 398. Random Pick Index | Medium | reservoir sampling |
| 523. Continuous Subarray Sum | Medium | accumulate sum |
| 525. Contiguous Array | Medium | accumulate sum |
| 332. Reconstruct Itinerary | Medium | use multiset and DFS |
| 323. Number of Connected Components in an Undirected Graph | Medium | build a adjacent list and DFS |
| 249. Group Shifted Strings | Medium | loop with visited |
| 382. Linked List Random Node | Meidum | reservoir sampling |
| stock系列 121 & 122 & 309 & 714 & 123 & 188 | Easy&Medium&Hard | Dp |
| 316. Remove Duplicate Letters | Hard | used map and loop, read detail |
| 289. Game of Life | Medium | traverse and change the value |
| 164. Maximum Gap | Hard | Bucket sort |
| 804. Unique Morse Code Words | Easy | Using set and vectors |
| 220. Contains Duplicate III | Medium | Using sliding windows and maps |
| 335. Self Crossing | Hard | Enum all possible situations |
| 233. Number of Digit One | Hard | Find its patter |
| 179. Largest Number | Medium | Sort by new comparator |
| 229. Majority Element II | Medium | Moore voting |
| 169. Majority Element | Easy | Moore voting |
| 540. Single Element in a Sorted Array | Medium | Binary Search |
| 419. Battleships in a Board | Medium | traverse and judge |
| 150. Evaluate Reverse Polish Notation | Medium | stack |
| 53. Find Minimum in Rotated Sorted Array | Easy | Binary search |
| 319. Bulb Switcher | Medium | observe the previous results and do math |
| 223. Rectangle Area | Medium | do math |
| 479. Largest Palindrome Product | Easy | do math |
| 219. Contains Duplicate II | Easy | map !!careful!! |
| 438. Find All Anagrams in a String | Easy | sliding window |
| 406. Queue Reconstruction by Height | Medium | analysis the problems |
| 581. Shortest Unsorted Continuous Subarray | Easy | read detail:) |
| 416. Partition Equal D Sum | Medium | DP |
| 124. Binary Tree Maximum Path Sum | Medium | traverse by recursion |
| 240. Search a 2D Matrix II | Medim | Find the special corner as start |
| 160. Intersection of Two Linked Lists | Easy | check from the same length |
| 6. ZigZag Conversion | Medium | find relationships or store in arrays |
| 172. Factorial Trailing Zeroes | Easy | find number of 5 |
| 152. Maximum Product Subarray | Medium | using 2(max, min) help array |
| 149. Max Points on a Line | Hard | use map and cal gcd |
| 22. Generate Parentheses | Medium | DFS + limits |
| 328. Odd Even Linked List | Medium | pointers |
| 338. Counting Bits | Meidum | loop with vector |
| 293. Flip Game && 294. Flip Game II | Easy & Medium | back tracking |
| 292. Nim Game | Easy | Game Theory |
| 4. Median of Two Sorted Arrays | Hard | with 2 pointers |
| 209. Minimum Size Subarray Sum | Medium | sliding window |
| 322. Coin Change | Medium | DP |
| 673. Number of Longest Increasing Subsequence | Medium | with 2 record vector read details :) |
| 287. Find the duplicate Number | Meidum | binary search and fast and slow pointer |
| 377. Combination Sum IV | Meidum | DP |
| 89. Gray Code | Medium | details:) |
| 43. Multiply Strings | Medium | use array to store product |
| 143. Reorder List | Medium | break the list into 2 lists, process them |
| 57. Insert Interval | Hard | details :) |
| 76. Minimum Window Substring | Hard | Sliding Window |
| 285. Inorder Successor in BST | Medium | characteristic of BST, or In-order traverse |
| 161. One Edit Distance | Medium | Consider corner situations |
| 311. Sparse Matrix Multiplication | Medium | pre-process one matrix |
| 494. Target Sum | Medium | DFS with memory searching to optimize |
| 670. Maximum Swap | Medium | find the maximum of its right including itself |
| 157. Read N Characters Given Read4 | Easy | read detail:) |
| 680. Valid Palindrome II | Easy | optimal bruce force |
| 314. Binary Tree Vertical Order Traversal | Medium | Level order traverse + map |
| 325. Maximum Size Subarray Sum Equals k | Medium | accumulate sum + hashmap |
| 253. Meeting Rooms II | Medium | heap(priority_queue) |
| 621. Task Scheduler | Medium | greedy & queue / mathematics |
| 277. Find the Celebrity | Medium | read details:) |
| 273. Integer to English Words | Hard | use map |
| 301. Remove Invalid Parentheses | Hard | BFS / recursion |
| 128. Longest Consecutive Sequence | Hard | use set |
| 236. Lowest Common Ancestor of a Binary Tree | Medium | PreOrder traverse with stack and pruning |
| 168. Excel Sheet Column Title | Easy | loop and reverse() |
| 127. Word Ladder | Medium | BFS, uses queue and map to help |
| 560. Subarray Sum Equals K | Medium | use map store the times of sum appears |
| 647. Palindromic Substrings | Medium | check every possible |
| 151. Reverse Words in a String | Medium | STL: reverse() |
| 535. Encode and Decode TinyURL | Medium | HashMap + rand() |
| 297. Serialize and Deserialize Binary Tree | Hard | iostream |
| 208. Implement Trie (Prefix Tree) | Medium | Trie tree |
| 146. LRU Cache | Hard | Hashmap + list + iterator |
| 632. Smallest Range | Hard | |
| 134. Gas Station | Medium | Greedy |
| 692. Top K Frequent Words | Medium | HashMap+pair |
| 347. Top K Frequent Elements | Medium | HashMap+pair |
| 106. Construct Binary Tree from Inorder and Postorder Traversal | Medium | recursion |
| 105. Construct Binary Tree from Preorder and Inorder Traversal | Medium | recursion |
| 81. Search in Rotated Sorted Array II | Medium | binary search |
| 33. Search in rotated sorted array | Medium | binary search |
| 120. Triangle | Medium | |
| 391. Perfect Rectangle | Hard | using the area and 4 points |
| 97. Interleaving String | Hard | dp |
| 45. Jump Game II | Hard | greedy |
| 148. Sort List | Medium | merge sort |
| 59. Spiral Matrix II | Medium | |
| 147. Insertion Sort List | Medium | insertion sort |
| 73. Set Matrix Zeroes | Medium | |
| 189. Rotate Array | Easy | |
| 118. Pascal's Triangle && 119. Pascal's Triangle II | Easy | queue |
| 90. Subsets II | Medium | |
| 78. Subsets | Medium | |
| 93. Restore IP Addresses | Medium | DFS |
| 71. Simplify Path | Medium | sstream |
| 82. Remove Duplicates from Sorted List II | Medium | pointer |
| 26.Remove Duplicates from Sorted Array | Easy | pointer |
| 95. Unique Binary Search Trees II | Medium | DFS / DP |
| 96. Unique Binary Search Trees | Medium | DP |
| 312. Burst Balloons | Hard | DP（区间DP） |
| 99. Recover Binary Search Tree | Hard | Inorder traverse |
| 98. Validate Binary Search Tree | Medium | Inorder traverse |
| 30. Substring with Concatenation of All Words | Hard | DFS + HashMap |
| 29. Divide Two Integers | Medium | bit operation |
| 443. String Compression | Easy | |
| 92. Reverse Linked List II | Medium | |
| 114. Flatten Binary Tree to Linked List | Medium | stack |
| 814. Binary Tree Pruning | Medium | |
| 324. Wiggle Sort II | Medium | |
| 341. Flatten Nested List Iterator | Medium | stack |
| 300. Longest Increasing Subsequence | Medium | |
| 72. Edit Distance | Hard | DP |
| 63. Unique Paths II | Medium | DP |
| 221.Maximal Square | Medium | |
| House Robbers. 198 & 213 | Medium & Easy | DP |
| 218.The Skyline Problem | Hard | scan line problem: heap |
| 41. First Missing Positive | Hard | interesting method |
| 138. Copy List with Random Pointer | Medium | map / list operation |
| 278. First Bad Version | Easy | binary search |
| 69. Sqrt(x) | Easy | binary search |
| 162. Find Peak Element | Medium | binary search |
| 239. Sliding Window Maximum | Hard | heap/deque |
| 654. Maximum Binary Tree | Medium | |
| 85. Maximal Rectangle | hard | |
| 36. Valid Sudoku | Medium | record matrix |
| 32. Longest Valid Parentheses | Hard | stack |
| 61. Rotated List | Medium | |
| leetcode栈系列155 & 232 & 349 | Easy | stack / 2 stacks |
| 480. Sliding Window Median | Hard | 2 heaps |
| 295. Find Median From Data Stream | Hard | 2 heaps |
| 84. Large rectangle in histogram | Hard | monotonous stack |
| 34. Search for a Range | Medium | |
| 44.wildcard matching | Hard | DP |
| 48. Rotate Image | Medium | |
| 49. Group Anagrams | Medium | hashmap |
| 10.Regular Expression Matching | Hard | recursion/DP |
| 25. Reverse Node in k-Group | Hard | |
| Leetcode Combination系列：39 & 77 & 40 & 216 & 17 | Medium | DFS |
| 38. Count and Say | Easy | |
| 35. search Insert Position | Easy | |
| 46.Permutation & 47.Permutation II |
Medium | DFS |
| 5 Longest Palindromic Substring | Medium | Manarch / common |
| 12. Integer to Roman | Medium | |
| 13. Roman to Integer | Easy | Hash-Map |
| 8. String to Integer | Medium | |
| 42. Trapping Rain Water | Hard | |
| 407. trapping rain water II | Hard | heap |
| 11. Container with Most Water | Medium | |
| 19 Remove Nth Node From End of List | Medium | fast and slow pointers |
| 23. Merge K sorted List | Hard | heap |
| 234. Palindrome Linked List | Easy | stack |
| 142. LinkedList Cycle II | Medium | fast and slow pointers |
| 141.Linked List Cycle 快慢指针 | Easy | fast and slow pointers |
| leetcode Sum合集 | Easy & Medium | map |
| 79.word search | Medium | DFS with visited array |
| 261.Graph Valid Tree | Medium | Union Find to find circle |
| 305.Number Of Islands II | Hard | Union Find |