| 1. Two Sum | Easy | ArrayHash Table |
| 2. Add Two Numbers | Medium | Linked ListMathRecursion |
| 3. Longest Substring Without Repeating Characters | Medium | Hash TableStringSliding Window |
| 5. Longest Palindromic Substring | Medium | Two PointersStringDynamic Programming |
| 11. Container With Most Water | Medium | ArrayTwo PointersGreedy |
| 15. 3Sum | Medium | ArrayTwo PointersSorting |
| 16. 3Sum Closest | Medium | ArrayTwo PointersSorting |
| 18. 4Sum | Medium | ArrayTwo PointersSorting |
| 19. Remove Nth Node From End of List | Medium | Linked ListTwo Pointers |
| 20. Valid Parentheses | Easy | StringStack |
| 21. Merge Two Sorted Lists | Easy | Linked ListRecursion |
| 22. Generate Parentheses | Medium | StringDynamic ProgrammingBacktracking |
| 23. Merge k Sorted Lists | Hard | Linked ListDivide and ConquerHeap (Priority Queue)+1 more |
| 33. Search in Rotated Sorted Array | Medium | ArrayBinary Search |
| 39. Combination Sum | Medium | ArrayBacktracking |
| 40. Combination Sum II | Medium | ArrayBacktracking |
| 42. Trapping Rain Water | Hard | ArrayTwo PointersDynamic Programming+2 more |
| 45. Jump Game II | Medium | ArrayDynamic ProgrammingGreedy |
| 46. Permutations | Medium | ArrayBacktracking |
| 48. Rotate Image | Medium | ArrayMathMatrix |
| 49. Group Anagrams | Medium | ArrayHash TableString+1 more |
| 53. Maximum Subarray | Medium | ArrayDivide and ConquerDynamic Programming |
| 54. Spiral Matrix | Medium | ArrayMatrixSimulation |
| 55. Jump Game | Medium | ArrayDynamic ProgrammingGreedy |
| 56. Merge Intervals | Medium | ArraySorting |
| 57. Insert Interval | Medium | Array |
| 62. Unique Paths | Medium | MathDynamic ProgrammingCombinatorics |
| 70. Climbing Stairs | Easy | MathDynamic ProgrammingMemoization |
| 73. Set Matrix Zeroes | Medium | ArrayHash TableMatrix |
| 74. Search a 2D Matrix | Medium | ArrayBinary SearchMatrix |
| 76. Minimum Window Substring | Hard | Hash TableStringSliding Window |
| 78. Subsets | Medium | ArrayBacktrackingBit Manipulation |
| 79. Word Search | Medium | ArrayStringBacktracking+2 more |
| 90. Subsets II | Medium | ArrayBacktrackingBit Manipulation |
| 91. Decode Ways | Medium | StringDynamic Programming |
| 98. Validate Binary Search Tree | Medium | TreeDepth-First SearchBinary Search Tree+1 more |
| 100. Same Tree | Easy | TreeDepth-First SearchBreadth-First Search+1 more |
| 102. Binary Tree Level Order Traversal | Medium | TreeBreadth-First SearchBinary Tree |
| 103. Binary Tree Zigzag Level Order Traversal | Medium | TreeBreadth-First SearchBinary Tree |
| 104. Maximum Depth of Binary Tree | Easy | TreeDepth-First SearchBreadth-First Search+1 more |
| 105. Construct Binary Tree from Preorder and Inorder Traversal | Medium | ArrayHash TableDivide and Conquer+2 more |
| 106. Construct Binary Tree from Inorder and Postorder Traversal | Medium | ArrayHash TableDivide and Conquer+2 more |
| 110. Balanced Binary Tree | Easy | TreeDepth-First SearchBinary Tree |
| 112. Path Sum | Easy | TreeDepth-First SearchBreadth-First Search+1 more |
| 113. Path Sum II | Medium | BacktrackingTreeDepth-First Search+1 more |
| 114. Flatten Binary Tree to Linked List | Medium | Linked ListStackTree+2 more |
| 121. Best Time to Buy and Sell Stock | Easy | ArrayDynamic Programming |
| 122. Best Time to Buy and Sell Stock II | Medium | ArrayDynamic ProgrammingGreedy |
| 124. Binary Tree Maximum Path Sum | Hard | Dynamic ProgrammingTreeDepth-First Search+1 more |
| 127. Word Ladder | Hard | Hash TableStringBreadth-First Search |
| 128. Longest Consecutive Sequence | Medium | ArrayHash TableUnion-Find |
| 130. Surrounded Regions | Medium | ArrayDepth-First SearchBreadth-First Search+2 more |
| 133. Clone Graph | Medium | Hash TableDepth-First SearchBreadth-First Search+1 more |
| 139. Word Break | Medium | ArrayHash TableString+3 more |
| 141. Linked List Cycle | Easy | Hash TableLinked ListTwo Pointers |
| 143. Reorder List | Medium | Linked ListTwo PointersStack+1 more |
| 146. LRU Cache | Medium | Hash TableLinked ListDesign+1 more |
| 150. Evaluate Reverse Polish Notation | Medium | ArrayMathStack |
| 152. Maximum Product Subarray | Medium | ArrayDynamic Programming |
| 153. Find Minimum in Rotated Sorted Array | Medium | ArrayBinary Search |
| 155. Min Stack | Medium | StackDesign |
| 167. Two Sum II - Input Array Is Sorted | Medium | ArrayTwo PointersBinary Search |
| 169. Majority Element | Easy | ArrayHash TableDivide and Conquer+2 more |
| 198. House Robber | Medium | ArrayDynamic Programming |
| 199. Binary Tree Right Side View | Medium | TreeDepth-First SearchBreadth-First Search+1 more |
| 200. Number of Islands | Medium | ArrayDepth-First SearchBreadth-First Search+2 more |
| 206. Reverse Linked List | Easy | Linked ListRecursion |
| 207. Course Schedule | Medium | Depth-First SearchBreadth-First SearchGraph Theory+1 more |
| 208. Implement Trie (Prefix Tree) | Medium | Hash TableStringDesign+1 more |
| 210. Course Schedule II | Medium | Depth-First SearchBreadth-First SearchGraph Theory+1 more |
| 211. Design Add and Search Words Data Structure | Medium | StringDepth-First SearchDesign+1 more |
| 212. Word Search II | Hard | ArrayStringBacktracking+2 more |
| 213. House Robber II | Medium | ArrayDynamic Programming |
| 215. Kth Largest Element in an Array | Medium | ArrayDivide and ConquerSorting+2 more |
| 217. Contains Duplicate | Easy | ArrayHash TableSorting |
| 226. Invert Binary Tree | Easy | TreeDepth-First SearchBreadth-First Search+1 more |
| 230. Kth Smallest Element in a BST | Medium | TreeDepth-First SearchBinary Search Tree+1 more |
| 235. Lowest Common Ancestor of a Binary Search Tree | Medium | TreeDepth-First SearchBinary Search Tree+1 more |
| 236. Lowest Common Ancestor of a Binary Tree | Medium | TreeDepth-First SearchBinary Tree |
| 238. Product of Array Except Self | Medium | ArrayPrefix Sum |
| 239. Sliding Window Maximum | Hard | ArrayQueueSliding Window+2 more |