| No. | Problem | Difficulty |
|---|---|---|
| 1 | Symmetric Tree | Easy |
| 2 | Invert Binary Tree | Easy |
| 3 | Sum Root to Leaf Numbers | Medium |
| 4 | Maximum Depth of Binary Tree | Easy |
| 5 | Minimum Depth of Binary Tree | Easy |
| 6 | Binary-tree-preorder-traversal | Easy |
| 7 | Binary-tree-inorder-traversal | Easy |
| 8 | Binary-tree-postorder-traversal | Easy |
| 9 | Balance-a-binary-search-tree | Medium |
| 10 | Binary-search-tree-to-greater-sum-tree | Medium |
| 11 | Validate-binary-search-tree | Medium |
| 12 | Sum-root-to-leaf-numbers | Medium |
| 13 | Sum-of-root-to-leaf-binary-numbers | Easy |
| 14 | Count-complete-tree-nodes | Easy |
| 15 | Path-sum | Easy |
| 16 | Path-sum-ii | Medium |
| 17 | Kth-largest-sum-in-a-binary-tree | Medium |