| 222 | Count Complete Tree Nodes | Medium |
| 230 | Kth Smallest Element in a BST | Medium |
| 235 | Lowest Common Ancestor of a Binary Search Tree | Easy |
| 236 | Lowest Common Ancestor of a Binary Tree | Medium |
| 257 | Binary Tree Paths | Easy |
| 297 | Serialize and Deserialize Binary Tree | Hard |
| 331 | Verify Preorder Serialization of a Binary Tree | Medium |
| 337 | House Robber III | Medium |
| 404 | Sum of Left Leaves | Easy |
| 437 | Path Sum III | Medium |
| 449 | Serialize and Deserialize BST | Medium |
| 450 | Delete Node in a BST | Medium |
| 501 | Find Mode in Binary Search Tree | Easy |
| 508 | Most Frequent Subtree Sum | Medium |
| 513 | Find Bottom Left Tree Value | Medium |
| 515 | Find Largest Value in Each Tree Row | Medium |
| 530 | Minimum Absolute Difference in BST | Easy |
| 538 | Convert BST to Greater Tree | Medium |
| 543 | Diameter of Binary Tree | Easy |
| 563 | Binary Tree Tilt | Easy |
| 572 | Subtree of Another Tree | Easy |
| 606 | Construct String from Binary Tree | Easy |
| 637 | Average of Levels in Binary Tree | Easy |
| 652 | Find Duplicate Subtrees | Medium |
| 653 | Two Sum IV - Input is a BST | Easy |
| 654 | Maximum Binary Tree | Medium |
| 655 | Print Binary Tree | Medium |
| 662 | Maximum Width of Binary Tree | Medium |
| 671 | Second Minimum Node In a Binary Tree | Easy |
| 687 | Longest Univalue Path | Medium |