| 2. Add Two Numbers | | | Solve | Medium | | |
| 3. Longest Substring Without Repeating Characters | | | Solve | Medium | | |
| 5. Longest Palindromic Substring | | | Solve | Medium | | |
| 7. Reverse Integer | | | Solve | Medium | | |
| 15. 3Sum | | | Solve | Medium | | |
| 17. Letter Combinations of a Phone Number | | | Solve | Medium | | |
| 22. Generate Parentheses | | | Solve | Medium | | |
| 33. Search in Rotated Sorted Array | | | Solve | Medium | | |
| 34. Find First and Last Position of Element in Sorted Array | | | Solve | Medium | | |
| 40. Combination Sum II | | | Solve | Medium | | |
| 46. Permutations | | | Solve | Medium | | |
| 49. Group Anagrams | | | Solve | Medium | | |
| 50. Pow(x, n) | | | Solve | Medium | | |
| 53. Maximum Subarray | | | Solve | Medium | | |
| 54. Spiral Matrix | | | Solve | Medium | | |
| 56. Merge Intervals | | | Solve | Medium | | |
| 62. Unique Paths | | | Solve | Medium | | |
| 63. Unique Paths II | | | Solve | Medium | | |
| 64. Minimum Path Sum | | | Solve | Medium | | |
| 74. Search a 2D Matrix | | | Solve | Medium | | |
| 92. Reverse Linked List II | | | Solve | Medium | | |
| 98. Validate Binary Search Tree | | | Solve | Medium | | |
| 102. Binary Tree Level Order Traversal | | | Solve | Medium | | |
| 103. Binary Tree Zigzag Level Order Traversal | | | Solve | Medium | | |
| 113. Path Sum II | | | Solve | Medium | | |
| 116. Populating Next Right Pointers in Each Node | | | Solve | Medium | | |
| 122. Best Time to Buy and Sell Stock II | | | Solve | Medium | | |
| 139. Word Break | | | Solve | Medium | | |
| 146. LRU Cache | | | Solve | Medium | | |
| 150. Evaluate Reverse Polish Notation | | | Solve | Medium | | |
| 153. Find Minimum in Rotated Sorted Array | | | Solve | Medium | | |
| 155. Min Stack | | | Solve | Medium | | |
| 172. Factorial Trailing Zeroes | | | Solve | Medium | | |
| 176. Second Highest Salary | | | Solve | Medium | | |
| 179. Largest Number | | | Solve | Medium | | |
| 199. Binary Tree Right Side View | | | Solve | Medium | | |
| 200. Number of Islands | | | Solve | Medium | | |
| 207. Course Schedule | | | Solve | Medium | | |
| 208. Implement Trie (Prefix Tree) | | | Solve | Medium | | |
| 215. Kth Largest Element in an Array | | | Solve | Medium | | |
| 227. Basic Calculator II | | | Solve | Medium | | |
| 236. Lowest Common Ancestor of a Binary Tree | | | Solve | Medium | | |
| 238. Product of Array Except Self | | | Solve | Medium | | |
| 240. Search a 2D Matrix II | | | Solve | Medium | | |
| 253. Meeting Rooms II | | | Solve | Medium | | |
| 255. Verify Preorder Sequence in Binary Search Tree | | | Solve | Medium | | |
| 300. Longest Increasing Subsequence | | | Solve | Medium | | |
| 316. Remove Duplicate Letters | | | Solve | Medium | | |
| 333. Largest BST Subtree | | | Solve | Medium | | |
| 347. Top K Frequent Elements | | | Solve | Medium | | |
