| 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 |
| 341 | Flatten Nested List Iterator | Medium |
| 404 | Sum of Left Leaves | Easy |
| 427 | Construct Quad Tree | Medium |
| 429 | N-ary Tree Level Order Traversal | Medium |
| 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 |
| 558 | Logical OR of Two Binary Grids Represented as Quad-Trees | Medium |
| 559 | Maximum Depth of N-ary Tree | Easy |
| 563 | Binary Tree Tilt | Easy |
| 572 | Subtree of Another Tree | Easy |
| 589 | N-ary Tree Preorder Traversal | Easy |
| 590 | N-ary Tree Postorder Traversal | Easy |
| 606 | Construct String from Binary Tree | Easy |
| 617 | Merge Two Binary Trees | Easy |
| 623 | Add One Row to Tree | Medium |