| 20 | Valid Parentheses | Easy |
| 42 | Trapping Rain Water | Hard |
| 71 | Simplify Path | Medium |
| 84 | Largest Rectangle in Histogram | Hard |
| 85 | Maximal Rectangle | Hard |
| 94 | Binary Tree Inorder Traversal | Medium |
| 103 | Binary Tree Zigzag Level Order Traversal | Medium |
| 144 | Binary Tree Preorder Traversal | Medium |
| 145 | Binary Tree Postorder Traversal | Hard |
| 150 | Evaluate Reverse Polish Notation | Medium |
| 155 | Min Stack | Easy |
| 173 | Binary Search Tree Iterator | Medium |
| 224 | Basic Calculator | Hard |
| 232 | Implement Queue using Stacks | Easy |
| 316 | Remove Duplicate Letters | Hard |
| 341 | Flatten Nested List Iterator | Medium |
| 445 | Add Two Numbers II | Medium |
| 456 | 132 Pattern | Medium |
| 496 | Next Greater Element I | Easy |
| 503 | Next Greater Element II | Medium |
| 654 | Maximum Binary Tree | Medium |
| 735 | Asteroid Collision | Medium |
| 739 | Daily Temperatures | Medium |
| 844 | Backspace String Compare | Easy |
| 880 | Decoded String at Index | Medium |
| 907 | Sum of Subarray Minimums | Medium |
| 1047 | Remove All Adjacent Duplicates In String | Easy |
| 1441 | Build an Array With Stack Operations | Medium |
| 1475 | Final Prices With a Special Discount in a Shop | Easy |
| 1544 | Make The String Great | Easy |