从开始这个Github已经有将近两年时间, 很高兴这个repo可以帮到有需要的人. 我一直认为, 知识本身是无价的, 因此每逢闲暇, 我就会来维护这个repo, 给刷题的朋友们一些我的想法和见解. 下面来简单介绍一下这个repo:
README.md: 所有所做过的题目
ReviewPage.md: 所有题目的总结和归纳（不断完善中）
KnowledgeHash2.md: 对所做过的知识点的一些笔记
SystemDesign.md: 对系统设计的一些笔记
Future Milestone: 我准备将一些有意思的题目，做成视频的形式给大家参考
希望大家学习顺利, 对未来充满希望(程序员也是找到好老板的!) 有问题可以给我写邮件(wangdeve@gmail.com), 或者在GitHub上发issue给我.
| Squence | Problem | Level | Language | Tags | Video Tutorial |
|---|---|---|---|---|---|
| 0 | Binary Representation.java | Hard | Java | [] | |
| 1 | Binary Tree Zigzag Level Order Traversal.java | Medium | Java | [BFS, Stack, Tree] | |
| 2 | Count of Smaller Number before itself.java | Hard | Java | [] | |
| 3 | Count of Smaller Number.java | Review | Java | [Binary Search, Segment Tree] | |
| 4 | Delete Digits.java | Medium | Java | [] | |
| 5 | Find the Weak Connected Component in the Directed Graph.java | Medium | Java | [Union Find] | |
| 6 | Flatten 2D Vector.java | Medium | Java | [Design] | |
| 7 | Fraction to Recurring Decimal.java | Medium | Java | [Hash Table, Math] | |
| 8 | Gray Code.java | Medium | Java | [Backtracking] | |
| 9 | Group Shifted Strings.java | Easy | Java | [] | |
| 10 | H-Index.java | Medium | Java | [Hash Table, Sort] | |
| 11 | Hamming Distance.java | Easy | Java | [] | |
| 12 | Happy Number.java | Easy | Java | [] | |
| 13 | HashHeap.java | Hard | Java | [] | |
| 14 | HashWithArray.java | Easy | Java | [] | |
| 15 | Heapify.java | Review | Java | [Heap] | |
| 16 | Heaters.java | Easy | Java | [] | |
| 17 | IndexMatch.java | Easy | Java | [] | |
| 18 | Inorder Successor in Binary Search Tree.java | Medium | Java | [BST, Tree] | |
| 19 | Insert Node in a Binary Search Tree .java | Easy | Java | [BST] | |
| 20 | Intersection of Two Arrays.java | Easy | Java | [] | |
| 21 | Intersection of Two Linked Lists.java | Easy | Java | [Linked List] | |
| 22 | Interval Sum II.java | Hard | Java | [] | |
| 23 | Isomorphic Strings.java | Easy | Java | [] | |
| 24 | Jewels and Stones.java | Easy | Java | [Hash Table] | |
| 25 | Kth Largest Element.java | Review | Java | [Divide and Conquer, Heap, Quick Sort] | |
| 26 | Kth Smallest Sum In Two Sorted Arrays.java | Hard | Java | [] | |
| 27 | LFU Cache.java | Hard | Java | [Design, Hash Table] | |
| 28 | Longest Palindromic Substring.java | Review | Java | [DP, String] | |
| 29 | Longest Univalue Path.java | Easy | Java | [] | |
| 30 | Majority Number II.java | Medium | Java | [Enumeration, Greedy] | |
| 31 | Majority Number III.java | Medium | Java | [Hash Table, Linked List] | |
| 32 | Matrix Zigzag Traversal.java | Easy | Java | [] | |
| 33 | Max Area of Island.java | Easy | Java | [] | |
| 34 | Max Points on a Line.java | Hard | Java | [Array, Geometry, Hash Table] | |
| 35 | Maximum Subarray III.java | Review | Java | [] | |
| 36 | Minimum Absolute Difference in BST.java | Easy | Java | [BST] | |
| 37 | Minimum Height Trees.java | Medium | Java | [BFS, Graph] | |
| 38 | Minimum Subarray.java | Easy | Java | [Array, Greedy] | |
| 39 | Missing Ranges.java | Medium | Java | [Array] | |
| 40 | Multiply Strings.java | Medium | Java | [Math, String] | |
| 41 | Next Permutation.java | Medium | Java | [Array] | |
| 42 | O(1) Check Power of 2.java | Easy | Java | [Bit Manipulation] | |
| 43 | Paint Fence.java | Easy | Java | [] | |
| 44 | Palindrome Permutation II.java | Medium | Java | [Backtracking, Permutation] | |
| 45 | Partition Array by Odd and Even.java | Easy | Java | [Array, Two Pointers] | |
| 46 | Pascal's Triangle II.java | Easy | Java | [] | |
| 47 | Permutation Index.java | Easy | Java | [] | |
| 48 | Permutation Sequence.java | Medium | Java | [Backtracking, Math] | |
| 49 | Populating Next Right Pointers in Each Node II.java | Hard | Java | [] | |
| 50 | Product of Array Exclude Itself.java | Medium | Java | [Array] | |
| 51 | Recover Rotated Sorted Array.java | Easy | Java | [Array] | |
| 52 | Remove Duplicates from Unsorted List.java | Medium | Java | [Linked List] | |
| 53 | Remove Invalid Parentheses.java | Hard | Java | [] | |
| 54 | Remove Node in Binary Search Tree.java | Hard | Java | [BST] | |
| 55 | Reshape the Matrix.java | Easy | Java | [] | |
| 56 | Reverse String.java | Easy | Java | [] | |
| 57 | Roman to Integer.java | Easy | Java | [] | |
| 58 | Rotate Image.java | Medium | Java | [Array, Enumeration] | |
| 59 | Search Insert Position.java | Easy | Java | [] | |
| 60 | Search Rotated in Sorted Array II.java | Medium | Java | [Array, Binary Search] | |
| 61 | Search Rotated in Sorted Array.java | Hard | Java | [] | |
| 62 | Shortest Word Distance.java | Easy | Java | [] | |
| 63 | Single Number II.java | Medium | Java | [Bit Manipulation] | |
| 64 | Single Number III.java | Medium | Java | [Bit Manipulation] | |
| 65 | Single Number.java | Easy | Java | [] | |
| 66 | Sliding Window Maximum.java | Hard | Java | [] | |
| 67 | Sort Color.java | Medium | Java | [Array, Sort, Two Pointers] | |
| 68 | Sort Colors II.java | Medium | Java | [Sort, Two Pointers] | |
| 69 | Sort Letters by Case.java | Medium | Java | [Sort, String, Two Pointers] | |
| 70 | Space Replacement.java | Medium | Java | [String] | |
| 71 | Stone Game.java | Medium | Java | [DP] | |
| 72 | String Permutation.java | Easy | Java | [] | |
| 73 | String to Integer(atoi).java | Easy | Java | [] | |
| 74 | Strobogrammatic Number.java | Easy | Java | [] | |
| 75 | Subarray Sum Closest.java | Medium | Java | [Sort] | |
| 76 | Subarray Sum.java | Easy | Java | [] | |
| 77 | The Smallest Difference.java | Medium | Java | [Array, Sort, Two Pointers] | |
| 78 | Total Occurrence of Target.java | Medium | Java | [] | |
| 79 | Trailing Zeros.java | Easy | Java | [Math] | |
| 80 | Triangles.java | Medium | Java | [Array, DP] | |
| 81 | Two Lists Sum.java | Medium | Java | [Linked List] | |
| 82 | Two Strings Are Anagrams.java | Easy | Java | [] | |
| 83 | Ugly Number II.java | Medium | Java | [DP, Heap, Math] | |
| 84 | Valid Parentheses.java | Easy | Java | [] | |
| 85 | Valid Sudoku.java | Easy | Java | [] | |
| 86 | Word Ladder II.java | Hard | Java | [] | |
| 87 | Word Pattern.java | Easy | Java | [] | |
| 88 | Zigzag Iterator.java | Medium | Java | [BST] | |
| 89 | Find Anagram Mappings.java | Easy | Java | [Hash Table] | |
| 90 | Judge Route Circle.java | Easy | Java | [String] | |
| 91 | Island Perimeter.java | Easy | Java | [Hash Table] | |
| 92 | First Unique Character in a String.java | Easy | Java | [Hash Table, String] | |
| 93 | Power of Three.java | Easy | Java | [Math] | |
| 94 | Plus One.java | Easy | Java | [Array, Math] | |
| 95 | Power of Two.java | Easy | Java | [Bit Manipulation, Math] | |
| 96 | Reverse Vowels of a String.java | Easy | Java | [String, Two Pointers] | |
| 97 | Guess Number Higher or Lower.java | Easy | Java | [Binary Search] | |
| 98 | Encode and Decode TinyURL.java | Medium | Java | [Hash Table, Math] | |
| 99 | Wiggle Sort.java | Medium | Java | [Array, Sort] | |
| 100 | Queue Reconstruction by Height.java | Medium | Java | [Greedy] | |
| 101 | 2 Sum II - Input array is sorted.java | Medium | Java | [Array, Binary Search, Two Pointers] | |
| 102 | 2 Sum II.java | Medium | Java | [Array, Binary Search, Two Pointers] | |
| 103 | Coin Change.java | Medium | Java | [DP, Memoization, Sequence DP] | |
| 104 | Maximum Product Subarray.java | Medium | Java | [Array, DP] | |
| 105 | 3 Sum Closest.java | Medium | Java | [Array, Two Pointers] | |
| 106 | Triangle Count.java | Medium | Java | [Array] | |
| 107 | 3 Sum.java | Medium | Java | [Array, Two Pointers] | |
| 108 | 4 Sum.java | Medium | Java | [Hash Table] | |
| 109 | k Sum.java | Hard | Java | [DP] | |
| 110 | Longest Increasing Subsequence.java | Medium | Java | [Binary Search, Coordinate DP, DP, Memoization, Sequence DP] | |
| 111 | Unique Binary Search Tree.java | Medium | Java | [BST, DP, Tree] | |
| 112 | Trim a Binary Search Tree.java | Easy | Java | [BST, Tree] | |
| 113 | Unique Paths II.java | Medium | Java | [Array, Coordinate DP, DP] | |
| 114 | Bomb Enemy.java | Medium | Java | [Coordinate DP, DP] | |
| 115 | 3 Sum Smaller.java | Medium | Java | [Array, Two Pointers] | |
| 116 | Array Partition I.java | Easy | Java | [Array] | |
| 117 | 1-bit and 2-bit Characters.java | Easy | Java | [Array] | |
| 118 | Non-decreasing Array.java | Easy | Java | [Array] | |
| 119 | Max Consecutive Ones.java | Easy | Java | [Array] | |
| 120 | Find All Numbers Disappeared in an Array.java | Easy | Java | [Array] | |
| 121 | Maximum Average Subarray I.java | Easy | Java | [Array] | |
| 122 | Largest Number At Least Twice of Others.java | Easy | Java | [Array] | |
| 123 | Toeplitz Matrix.java | Easy | Java | [Array] | |
| 124 | Sum of Two Integers.java | Easy | Java | [Bit Manipulation] | |
| 125 | Swap Bits.java | Easy | Java | [Bit Manipulation] | |
| 126 | Update Bits.java | Medium | Java | [Bit Manipulation] | |
| 127 | Maximum XOR of Two Numbers in an Array.java | Medium | Java | [Bit Manipulation, Trie] | |
| 128 | Perfect Squares.java | Medium | Java | [BFS, DP, Math, Partition DP] | |
| 129 | Backpack VI.java | Medium | Java | [Backpack DP, DP] | |
| 130 | Copy Books.java | Hard | Java | [Binary Search, DP, Partition DP] | |
| 131 | Valid Perfect Square.java | Review | Java | [Binary Search, Math] | |
| 132 | Intersection of Two Arrays II.java | Easy | Java | [Binary Search, Hash Table, Sort, Two Pointers] | |
| 133 | Longest Palindromic Subsequence.java | Medium | Java | [DP, Interval DP, Memoization] | |
| 134 | Scramble String.java | Hard | Java | [DP, Interval DP, String] | |
| 135 | Binary Search Tree Iterator.java | Medium | Java | [BST, Design, Stack, Tree] | |
| 136 | Flatten Nested List Iterator.java | Medium | Java | [Design, Stack] | |
| 137 | Best Time to Buy and Sell Stock with Cooldown.java | Medium | Java | [DP] | |
| 138 | Find Peak Element.java | Medium | Java | [Array, Binary Search] | |
| 139 | Longest Common Subsequence.java | Medium | Java | [DP, Double Sequence DP] | |
| 140 | Interleaving String.java | Hard | Java | [DP, String] | |
| 141 | Letter Combinations of a Phone Number.java | Medium | Java | [Backtracking, String] | |
| 142 | Edit Distance.java | Hard | Java | [DP, Double Sequence DP, String] | |
| 143 | Distinct Subsequences.java | Hard | Java | [DP, String] | |
| 144 | Regular Expression Matching.java | Review | Java | [Backtracking, DP, String] | |
| 145 | Majority Element.java | Easy | Java | [Array, Bit Manipulation, Divide and Conquer] | |
| 146 | Wildcard Matching.java | Hard | Java | [Backtracking, DP, Greedy, String] | |
| 147 | Ones and Zeroes.java | Hard | Java | [DP] | |
| 148 | Pow(x,n).java | Medium | Java | [Binary Search, Math] | |
| 149 | Word Break II.java | Hard | Java | [Backtracking, DFS, DP, Memoization] | |
| 150 | Nested List Weight Sum.java | Easy | Java | [BFS, DFS] | |
| 151 | Same Tree.java | Easy | Java | [DFS, Tree] | |
| 152 | Convert Sorted Array to Binary Search Tree.java | Easy | Java | [DFS, Divide and Conquer, Tree] | |
| 153 | Construct Binary Tree from Inorder and Preorder Traversal.java | Medium | Java | [Array, DFS, Divide and Conquer, Hash Table, Tree] | |
| 154 | Add Binary.java | Easy | Java | [Math, String] | |
| 155 | Add Digits.java | Easy | Java | [Math] | |
| 156 | Add Two Numbers.java | Medium | Java | [Linked List, Math] | |
| 157 | Add Two Numbers II.java | Medium | Java | [Linked List] | |
| 158 | Balanced Binary Tree.java | Medium | Java | [DFS, Tree] | |
| 159 | Valid Anagram.java | Easy | Java | [Hash Table, Sort] | |
| 160 | Populating Next Right Pointers in Each Node.java | Medium | Java | [DFS, Divide and Conquer, Tree] | |
| 161 | Validate Binary Search Tree.java | Medium | Java | [BST, DFS, Divide and Conquer, Tree] | |
| 162 | Convert Sorted List to Binary Search Tree.java | Medium | Java | [BST, DFS, Divide and Conquer, Linked List] | |
| 163 | Flatten Binary Tree to Linked List.java | Medium | Java | [Binary Tree, DFS] | |
| 164 | Binary Tree Paths.java | Easy | Java | [Backtracking, Binary Tree, DFS] | |
| 165 | Minimum Size Subarray Sum.java | Medium | Java | [Array, Binary Search, Two Pointers] | |
| 166 | Clone Graph.java | Medium | Java | [BFS, DFS, Graph] | |
| 167 | Longest Substring Without Repeating Characters.java | Medium | Java | [Hash Table, String, Two Pointers] | |
| 168 | Minimum Window Substring.java | Hard | Java | [Hash Table, String, Two Pointers] | |
| 169 | Linked List Cycle.java | Easy | Java | [Linked List, Two Pointers] | |
| 170 | Remove Nth Node From End of List.java | Medium | Java | [Linked List, Two Pointers] | |
| 171 | Longest Substring with At Most K Distinct Characters.java | Medium | Java | [Hash Table, String] | |
| 172 | Linked List Cycle II.java | Medium | Java | [Linked List, Two Pointers] | |
| 173 | Kth Smallest Number in Sorted Matrix.java | Medium | Java | [Binary Search, Heap] | |
| 174 | Find Minimum in Rotated Sorted Array.java | Medium | Java | [Array, Binary Search] | |
| 175 | Find Minimum in Rotated Sorted Array II.java | Hard | Java | [Array, Binary Search] | |
| 176 | Connecting Graph.java | Medium | Java | [Union Find] | |
| 177 | Connecting Graph II.java | Medium | Java | [Union Find] | |
| 178 | Connecting Graph III.java | Medium | Java | [Union Find] | |
| 179 | Number of Islands.java | Medium | Java | [BFS, DFS, Matrix DFS, Union Find] | |
| 180 | Number of Islands II.java | Hard | Java | [Union Find] | |
| 181 | Surrounded Regions.java | Medium | Java | [BFS, DFS, Matrix DFS, Union Find] | |
| 182 | Implement Trie.java | Medium | Java | [Design, Trie] | |
| 183 | Add and Search Word.java | Medium | Java | [Backtracking, Design, Trie] | |
| 184 | Word Search II.java | Hard | Java | [Backtracking, DFS, Trie] | |
| 185 | Word Search.java | Medium | Java | [Array, Backtracking] | |
| 186 | Word Squares.java | Hard | Java | [Backtracking, Trie] | |
| 187 | Trapping Rain Water.java | Hard | Java | [Array, Stack, Two Pointers] | |
| 188 | Trapping Rain Water II.java | Hard | Java | [BFS, Heap] | |
| 189 | Data Stream Median.java | Hard | Java | [Design, Heap] | |
| 190 | Sliding Window Median.java | Hard | Java | [Design, Heap] | |
| 191 | Min Stack.java | Easy | Java | [Design, Stack] | |
| 192 | Implement Queue using Stacks.java | Easy | Java | [Design, Stack] | |
| 193 | Decode String.java | Medium | Java | [DFS, Divide and Conquer, Stack] | |
| 194 | Largest Rectangle in Histogram.java | Hard | Java | [Array, Monotonous Stack, Stack] | |
| 195 | Maximum Binary Tree.java | Medium | Java | [Stack, Tree] | |
| 196 | Reverse Integer.java | Easy | Java | [Math] | |
| 197 | Swap Nodes in Pairs.java | Medium | Java | [Linked List] | |
| 198 | Find Peak Element II.java | Hard | Java | [Binary Search, DFS, Divide and Conquer] | |
| 199 | Sqrt(x).java | Easy | Java | [Binary Search, Math] | |
| 200 | First Bad Version.java | Easy | Java | [Binary Search] | |
| 201 | Wood Cut.java | Medium | Java | [Binary Search] | |
| 202 | Find the Duplicate Number.java | Medium | Java | [Array, Binary Search, Two Pointers] | |
| 203 | Palindrome Pairs.java | Hard | Java | [Hash Table, String, Trie] | |
| 204 | Game of Life.java | Medium | Java | [Array] | |
| 205 | Maximum Average Subarray II.java | Review | Java | [Array, Binary Search, PreSum] | |
| 206 | Meeting Rooms.java | Easy | Java | [Sort, Sweep Line] | |
| 207 | Number of Airplane in the sky.java | Medium | Java | [Array, Interval, Sort, Sweep Line] | |
| 208 | Meeting Rooms II.java | Medium | Java | [Greedy, Heap, Sort, Sweep Line] | |
| 209 | Building Outline.java | Review | Java | [Binary Indexed Tree, Divide and Conquer, Heap, Segment Tree, Sweep Line] | |
| 210 | Unique Path.java | Medium | Java | [Array, Coordinate DP, DP] | |
| 211 | Maximal Rectangle.java | Hard | Java | [Array, DP, Hash Table, Stack] | |
| 212 | Maximal Square.java | Medium | Java | [Coordinate DP, DP] | |
| 213 | Longest Increasing Path in a Matrix.java | Hard | Java | [Coordinate DP, DFS, DP, Memoization, Topological Sort] | |
| 214 | Coins in a Line.java | Medium | Java | [DP, Game Theory, Greedy] | |
| 215 | Coins in a Line II.java | Medium | Java | [Array, DP, Game Theory, Memoization, MiniMax] | |
| 216 | Binary Tree Inorder Traversal.java | Easy | Java | [Hash Table, Stack, Tree] | |
| 217 | Binary Tree Postorder Traversal.java | Medium | Java | [Stack, Tree, Two Stacks] | |
| 218 | Change to Anagram.java | Easy | Java | [String] | |
| 219 | Classical Binary Search.java | Easy | Java | [Binary Search] | |
| 220 | Climbing Stairs.java | Easy | Java | [DP, Memoization, Sequence DP] | |
| 221 | Coins in a Line III.java | Hard | Java | [Array, DP, Game Theory, Interval DP, Memoization] | |
| 222 | Closest Binary Search Tree Value.java | Easy | Java | [BST, Binary Search, Tree] | |
| 223 | Compare Version Numbers.java | Medium | Java | [String] | |
| 224 | Count Complete Tree Nodes.java | Medium | Java | [Binary Search, Tree] | |
| 225 | Course Schedule.java | Medium | Java | [BFS, Backtracking, DFS, Graph, Topological Sort] | |
| 226 | Course Schedule II.java | Medium | Java | [BFS, DFS, Graph, Topological Sort] | |
| 227 | Binary Tree Preorder Traversal.java | Easy | Java | [BFS, DFS, Stack, Tree] | |
| 228 | Closest Number in Sorted Array.java | Easy | Java | [Binary Search] | |
| 229 | Complete Binary Tree.java | Easy | Java | [BFS, Tree] | |
| 230 | Compare Strings.java | Easy | Java | [String] | |
| 231 | Contains Duplicate.java | Easy | Java | [Array, Hash Table] | |
| 232 | Contains Duplicate II.java | Easy | Java | [Array, Hash Table] | |
| 233 | Contains Duplicate III.java | Medium | Java | [BST] | |
| 234 | Burst Balloons.java | Hard | Java | [DP, Divide and Conquer, Interval DP, Memoization] | |
| 235 | Nim Game.java | Easy | Java | [Brainteaser, DP, Game Theory] | |
| 236 | Convert Integer A to Integer B.java | Easy | Java | [Bit Manipulation] | |
| 237 | Cosine Similarity.java | Easy | Java | [Basic Implementation] | |
| 238 | Count 1 in Binary.java | Easy | Java | [Bit Manipulation] | |
| 239 | Count and Say.java | Easy | Java | [Basic Implementation, String] | |
| 240 | One Edit Distance.java | Medium | Java | [String] | |
| 241 | K Edit Distance.java | Hard | Java | [DP, Double Sequence DP, Trie] | |
| 242 | Jump Game.java | Medium | Java | [Array, DP, Greedy] | |
| 243 | Coin Change 2.java | Medium | Java | [DP, Sequence DP] | |
| 244 | Paint House.java | Easy | Java | [DP, Sequence DP] | |
| 245 | Decode Ways.java | Medium | Java | [DP, Partition DP, String] | |
| 246 | Longest Continuous Increasing Subsequence.java | Easy | Java | [Array, Coordinate DP, DP] | |
| 247 | Minimum Path Sum.java | Medium | Java | [Array, Coordinate DP, DP] | |
| 248 | Counting Bits.java | Medium | Java | [Bit Manipulation, Bitwise DP, DP] | |
| 249 | Continuous Subarray Sum.java | Medium | Java | [Coordinate DP, DP, Math] | |
| 250 | House Robber.java | Easy | Java | [DP, Sequence DP] | |
| 251 | House Robber II.java | Medium | Java | [DP, Sequence DP] | |
| 252 | House Robber III.java | Medium | Java | [DFS, DP, Status DP, Tree] | |
| 253 | Paint House II.java | Hard | Java | [DP, Sequence DP] | |
| 254 | Best Time to Buy and Sell Stock I.java | Easy | Java | [Array, DP, Sequence DP] | |
| 255 | Best Time to Buy and Sell Stock II.java | Easy | Java | [Array, DP, Greedy, Sequence DP] | |
| 256 | Best Time to Buy and Sell Stock III .java | Hard | Java | [Array, DP, Sequence DP] | |
| 257 | Best Time to Buy and Sell Stock IV.java | Hard | Java | [DP, Sequence DP] | |
| 258 | Russian Doll Envelopes.java | Hard | Java | [Binary Search, Coordinate DP, DP] | |
| 259 | Jump Game II.java | Hard | Java | [Array, Coordinate DP, DP, Greedy] | |
| 260 | Palindrome Partitioning.java | Medium | Java | [Backtracking, DFS] | |
| 261 | Permutation in String.java | Medium | Java | [Two Pointers] | |
| 262 | Permutations II.java | Medium | Java | [Backtracking] | |
| 263 | Shuffle an Array.java | Medium | Java | [Permutation] | |
| 264 | Find All Anagrams in a String.java | Easy | Java | [Hash Table] | |
| 265 | Group Anagrams.java | Medium | Java | [Hash Table, String] | |
| 266 | Backpack.java | Medium | Java | [Backpack DP, DP] | |
| 267 | Backpack II.java | Medium | Java | [Backpack DP, DP] | |
| 268 | Backpack V.java | Medium | Java | [Backpack DP, DP] | |
| 269 | Count Primes.java | Easy | Java | [Hash Table, Math] | |
| 270 | Delete Node in a Linked List.java | Easy | Java | [Linked List] | |
| 271 | Excel Sheet Column Number.java | Easy | Java | [Math] | |
| 272 | Excel Sheet Column Title.java | Easy | Java | [Math] | |
| 273 | Flip Game.java | Easy | Java | [String] | |
| 274 | Expression Tree Build.java | Hard | Java | [Binary Tree, Expression Tree, Minimum Binary Tree, Stack] | |
| 275 | Expression Evaluation.java | Hard | Java | [Binary Tree, DFS, Expression Tree, Minimum Binary Tree, Stack] | |
| 276 | Convert Expression to Polish Notation.java | Hard | Java | [Binary Tree, DFS, Expression Tree, Stack] | |
| 277 | Convert Expression to Reverse Polish Notation.java | Hard | Java | [Binary Tree, DFS, Expression Tree, Stack] | |
| 278 | Evaluate Reverse Polish Notation.java | Medium | Java | [Stack] | |
| 279 | Decode Ways II.java | Hard | Java | [DP, Partition DP] | |
| 280 | Palindrome Partitioning II.java | Hard | Java | [DP, Partition DP] | |
| 281 | Backpack III.java | Hard | Java | [Backpack DP, DP] | |
| 282 | First Missing Positive.java | Hard | Java | [Array] | |
| 283 | Gas Station.java | Medium | Java | [Greedy] | |
| 284 | Implement strStr().java | Easy | Java | [String, Two Pointers] | |
| 285 | Insertion Sort List.java | Medium | Java | [Linked List, Sort] | |
| 286 | Integer to English Words.java | Hard | Java | [Math, String] | |
| 287 | Interleaving Positive and Negative Numbers.java | Medium | Java | [Two Pointers] | |
| 288 | Largest Number.java | Medium | Java | [Sort] | |
| 289 | Last Position of Target.java | Easy | Java | [Binary Search] | |
| 290 | Length of Last Word.java | Easy | Java | [String] | |
| 291 | Longest Common Substring.java | Medium | Java | [DP, Double Sequence DP, String] | |
| 292 | Longest Increasing Continuous subsequence.java | Easy | Java | [Array, Coordinate DP, DP] | |
| 293 | Longest Increasing Continuous subsequence II.java | Medium | Java | [Array, Coordinate DP, DP, Memoization] | |
| 294 | N-Queens.java | Hard | Java | [Backtracking] | |
| 295 | N-Queens II.java | Hard | Java | [Backtracking] | |
| 296 | Longest Words.java | Easy | Java | [Hash Map, String] | |
| 297 | Maximum Subarray.java | Easy | Java | [Array, DFS, DP, Divide and Conquer, PreSum, Sequence DP] | |
| 298 | Maximum Subarray II.java | Medium | Java | [Array, DP, Greedy, PreSum, Sequence DP] | |
| 299 | Median.java | Easy | Java | [Array, Quick Select, Quick Sort] | |
| 300 | Merge Sorted Array.java | Easy | Java | [Array, Two Pointers] | |
| 301 | Middle of Linked List.java | Easy | Java | [Linked List] | |
| 302 | Singleton.java | Easy | Java | [Design] | |
| 303 | Remove Linked List Elements.java | Easy | Java | [Linked List] | |
| 304 | Fibonacci.java | Easy | Java | [DP, Math, Memoization] | |
| 305 | Palindrome Linked List.java | Easy | Java | [Linked List, Two Pointers] | |
| 306 | Reverse Linked List.java | Easy | Java | [Linked List] | |
| 307 | Reverse Linked List II .java | Medium | Java | [Linked List] | |
| 308 | Palindrome Permutation.java | Easy | Java | [Hash Table] | |
| 309 | Valid Palindrome.java | Easy | Java | [String, Two Pointers] | |
| 310 | Implement Stack using Queues.java | Easy | Java | [Design, Stack] | |
| 311 | Implement Stack.java | Easy | Java | [Stack] | |
| 312 | Invert Binary Tree.java | Easy | Java | [BFS, DFS, Tree] | |
| 313 | Maximum Depth of Binary Tree.java | Easy | Java | [DFS, Tree] | |
| 314 | Minimum Depth of Binary Tree.java | Easy | Java | [BFS, DFS, Tree] | |
| 315 | Symmetric Tree.java | Easy | Java | [BFS, DFS, Tree] | |
| 316 | Tweaked Identical Binary Tree.java | Easy | Java | [DFS, Tree] | |
| 317 | Merge Two Binary Trees.java | Easy | Java | [DFS, Tree] | |
| 318 | Subtree.java | Easy | Java | [DFS, Tree] | |
| 319 | Lowest Common Ancestor of a Binary Tree.java | Medium | Java | [DFS, Tree] | |
| 320 | Lowest Common Ancestor II.java | Easy | Java | [Hash Table, Tree] | |
| 321 | Lowest Common Ancestor of a Binary Search Tree.java | Medium | Java | [BST, DFS, Tree] | |
| 322 | Merge Intervals.java | Medium | Java | [Array, Sort, Sweep Line] | |
| 323 | Hash Function.java | Easy | Java | [Hash Table] | |
| 324 | Merge Two Sorted Lists.java | Easy | Java | [Linked List] | |
| 325 | Missing Number.java | Easy | Java | [Array, Bit Manipulation, Math] | |
| 326 | LRU Cache.java | Hard | Java | [Design, Hash Table, Linked List] | |
| 327 | Remove Duplicates from Sorted Array.java | Easy | Java | [Array, Two Pointers] | |
| 328 | Remove Duplicates from Sorted Array II.java | Medium | Java | [Array, Two Pointers] | |
| 329 | Remove Duplicates from Sorted List.java | Easy | Java | [Linked List] | |
| 330 | Remove Duplicates from Sorted List II.java | Medium | Java | [Linked List] | |
| 331 | QuickSort.java | Medium | Java | [Sort] | |
| 332 | MergeSort.java | Medium | Java | [Merge Sort, Sort] | |
| 333 | Longest Word in Dictionary.java | Easy | Java | [Hash Table, Trie] | |
| 334 | Anagrams.java | Medium | Java | [Array, Hash Map] | |
| 335 | Binary Tree Level Order Traversal.java | Medium | Java | [BFS, DFS, Tree] | |
| 336 | Binary Tree Level Order Traversal II.java | Medium | Java | [BFS, Tree] | |
| 337 | Binary Tree Longest Consecutive Sequence II.java | Medium | Java | [DFS, Divide and Conquer, Double Recursive, Tree] | |
| 338 | Binary Tree Maximum Path Sum.java | Hard | Java | [DFS, DP, Tree, Tree DP] | |
| 339 | Path Sum.java | Easy | Java | [DFS, Tree] | |
| 340 | Path Sum II.java | Easy | Java | [Backtracking, DFS, Tree] | |
| 341 | Path Sum III.java | Easy | Java | [DFS, Double Recursive, Tree] | |
| 342 | Rotate String.java | Easy | Java | [String] | |
| 343 | Path Sum IV.java | Medium | Java | [DFS, Hash Map, Tree] | |
| 344 | Combinations.java | Medium | Java | [Backtracking, Combination, DFS] | |
| 345 | Combination Sum.java | Medium | Java | [Array, Backtracking, Combination, DFS] | |
| 346 | Combination Sum II.java | Medium | Java | [Array, Backtracking, Combination, DFS] | |
| 347 | Combination Sum III.java | Medium | Java | [Array, Backtracking, Combination, DFS] | |
| 348 | Combination Sum IV.java | Medium | Java | [Array, Backpack DP, DP] | |
| 349 | Subset.java | Medium | Java | [Array, BFS, Backtracking, Bit Manipulation, DFS] | |
| 350 | Subsets II.java | Medium | Java | [Array, BFS, Backtracking, DFS] | |
| 351 | Binary Tree Right Side View.java | Medium | Java | [BFS, DFS, Tree] | |
| 352 | Binary Tree Maximum Path Sum II.java | Medium | Java | [DFS, Tree] | |
| 353 | Rotate List.java | Medium | Java | [Linked List, Two Pointers] | |
| 354 | Basic Calculator.java | Hard | Java | [Binary Tree, Expression Tree, Math, Minimum Binary Tree, Stack] | |
| 355 | Longest Consecutive Sequence.java | Hard | Java | [Array, Hash Table, Union Find] | |
| 356 | Binary Tree Longest Consecutive Sequence.java | Medium | Java | [DFS, Divide and Conquer, Tree] | |
| 357 | Number of Connected Components in an Undirected Graph.java | Medium | Java | [BFS, DFS, Graph, Union Find] | |
| 358 | Graph Valid Tree.java | Medium | Java | [BFS, DFS, Graph, Union Find] | |
| 359 | Next Closest Time.java | Medium | Java | [Basic Implementation, Enumeration, String] | |
| 360 | Serilization and Deserialization Of Binary Tree.java | Hard | Java | [BFS, DFS, Design, Divide and Conquer, Tree] | |
| 361 | Partition Array.java | Medium | Java | [Array, Quick Sort, Sort, Two Pointers] | |
| 362 | Word Ladder.java | Medium | Java | [BFS] | |
| 363 | Word Break.java | Medium | Java | [DP, Sequence DP] | |
| 364 | Unique Word Abbreviation.java | Medium | Java | [Design, Hash Table] | |
| 365 | Unique Binary Search Tree II.java | Medium | Java | [BST, DP, Divide and Conquer, Tree] | |
| 366 | Ugly Number.java | Medium | Java | [Math] | |
| 367 | Top K Frequent Words.java | Medium | Java | [Hash Table, Heap, PriorityQueue, Trie] | |
| 368 | Segment Tree Build.java | Medium | Java | [Binary Tree, Divide and Conquer, Segment Tree] | |
| 369 | Segment Tree Build II.java | Medium | Java | [Binary Tree, Divide and Conquer, Segment Tree] | |
| 370 | Segment Tree Query.java | Medium | Java | [Binary Tree, DFS, Divide and Conquer, Segment Tree] | |
| 371 | Segment Tree Modify.java | Medium | Java | [Binary Tree, DFS, Divide and Conquer, Segment Tree] | |
| 372 | Segment Tree Query II.java | Medium | Java | [Binary Tree, DFS, Divide and Conquer, Segment Tree] | |
| 373 | Count of Smaller Numbers After Self.java | Review | Java | [BST, Binary Indexed Tree, Binary Search, Divide and Conquer, Segment Tree] | |
| 374 | ColorGrid.java | Medium | Java | [Design, Hash Table] | |
| 375 | Container With Most Water.java | Medium | Java | [Array, Two Pointers] | |
| 376 | Convert Binary Search Tree to Doubly Linked List.java | Medium | Java | [Linked List, Tree] | |
| 377 | Copy List with Random Pointer.java | Medium | Java | [Hash Table, Linked List] | |
| 378 | Encode and Decode Strings.java | Medium | Java | [String] | |
| 379 | Fast Power.java | Medium | Java | [DFS, Divide and Conquer] | |
| 380 | Find the Connected Component in the Undirected Graph.java | Medium | Java | [BFS, DFS] | |
| 381 | H-Index II.java | Medium | Java | [Binary Search] | |
| 382 | HashWithCustomizedClass(LinkedList).java | Medium | Java | [Hash Table] | |
| 383 | Interval Minimum Number.java | Medium | Java | [Binary Search, Divide and Conquer, Segment Tree] | |
| 384 | Interval Sum.java | Medium | Java | [Binary Search, Segment Tree] | |
| 385 | Kth Smallest Element in a BST.java | Medium | Java | [BST, DFS, Stack, Tree] | |
| 386 | Longest Common Prefix.java | Easy | Java | [String] | |
| 387 | Majority Element II.java | Medium | Java | [Array] | |
| 388 | Merge k Sorted Lists.java | Medium | Java | [Divide and Conquer, Heap, Linked List, PriorityQueue] | |
| 389 | Merge k Sorted Arrays.java | Medium | Java | [Heap, PriorityQueue] | |
| 390 | Permutations.java | Medium | Java | [Backtracking, DFS, Permutation] | |
| 391 | Partition List.java | Medium | Java | [Linked List, Two Pointers] | |
| 392 | Peeking Iterator.java | Medium | Java | [Design] | |
| 393 | Rehashing.java | Medium | Java | [Hash Table] | |
| 394 | Reorder List.java | Medium | Java | [Linked List] | |
| 395 | Restore IP Addresses.java | Medium | Java | [Backtracking, DFS, String] | |
| 396 | Reverse Words in a String.java | Medium | Java | [String] | |
| 397 | Reverse Words in a String II.java | Medium | Java | [String] | |
| 398 | Reverse Words in a String III.java | Easy | Java | [String] | |
| 399 | Search a 2D Matrix.java | Medium | Java | [Array, Binary Search] | |
| 400 | Search a 2D Matrix II.java | Medium | Java | [Binary Search, Divide and Conquer] | |
| 401 | Search for a Range.java | Medium | Java | [Array, Binary Search] | |
| 402 | Search Range in Binary Search Tree .java | Medium | Java | [BST, Binary Tree] | |
| 403 | Merge Sorted Array II.java | Easy | Java | [Array] | |
| 404 | Nth to Last Node in List.java | Easy | Java | [Linked List] | |
| 405 | Unique Characters.java | Easy | Java | [Array, String] | |
| 406 | Sort List.java | Medium | Java | [Divide and Conquer, Linked List, Merge Sort, Sort] | |
| 407 | Summary Ranges.java | Medium | Java | [Array] | |
| 408 | Top K Frequent Elements.java | Medium | Java | [Hash Table, Heap, PriorityQueue] | |
| 409 | Topological Sorting.java | Medium | Java | [BFS, DFS, Topological Sort] | |
| 410 | Median of two Sorted Arrays.java | Hard | Java | [Array, Binary Search, DFS, Divide and Conquer] | |
| 411 | Remove Duplicate Letters.java | Hard | Java | [Greedy, Hash Table, Stack] | |
| 412 | Spiral Matrix.java | Medium | Java | [Array, Enumeration] | |
| 413 | Expression Add Operators.java | Hard | Java | [Backtracking, DFS, Divide and Conquer, String] | |
| 414 | Insert Interval.java | Hard | Java | [Array, PriorityQueue, Sort] | |
| 415 | Shortest Palindrome.java | Hard | Java | [KMP, String] | |
| 416 | 2 Sum.java | Easy | Java | [Array, Hash Table] | |
| 417 | K Empty Slots.java | Hard | Java | [Array, BST, TreeSet] | |
| 418 | Count of Range Sum.java | Hard | Java | [BST, Divide and Conquer, Merge Sort, PreSum] | |
| 419 | Max Sum of Rectangle No Larger Than K.java | Hard | Java | [Array, BST, Binary Search, DP, Queue, TreeSet] | |
| 420 | Perfect Rectangle.java | Hard | Java | [Design, Geometry, Hash Table] | |
| 421 | Construct Binary Tree from Inorder and Postorder Traversal.java | Medium | Java | [Array, DFS, Divide and Conquer, Tree] | |
| 422 | Generate Parentheses.java | Medium | Java | [Backtracking, DFS, Sequence DFS, String] | |
| 423 | Strobogrammatic Number II.java | Medium | Java | [DFS, Math, Sequence DFS] | |
| 424 | Alien Dictionary.java | Hard | Java | [BFS, Backtracking, DFS, Graph, Topological Sort] | |
| 425 | Flip Game II.java | Medium | Java | [DFS, DP, backtracking] |