| 94. Binary Tree Inorder Traversal | Solution | Solve | Easy | | |
| 98. Validate Binary Search Tree | Solution | Solve | Medium | | |
| 99. Recover Binary Search Tree | Solution | Solve | Medium | | |
| 100. Same Tree | Solution | Solve | Easy | | |
| 101. Symmetric Tree | Solution | Solve | Easy | | |
| 104. Maximum Depth of Binary Tree | Solution | Solve | Easy | | |
| 110. Balanced Binary Tree | Solution | Solve | Easy | | |
| 111. Minimum Depth of Binary Tree | Solution | Solve | Easy | | |
| 112. Path Sum | Solution | Solve | Easy | | |
| 113. Path Sum II | Solution | Solve | Medium | | |
| 114. Flatten Binary Tree to Linked List | Solution | Solve | Medium | | |
| 116. Populating Next Right Pointers in Each Node | Solution | Solve | Medium | | |
| 117. Populating Next Right Pointers in Each Node II | Solution | Solve | Medium | | |
| 124. Binary Tree Maximum Path Sum | Solution | Solve | Hard | | |
| 129. Sum Root to Leaf Numbers | Solution | Solve | Medium | | |
| 130. Surrounded Regions | Solution | Solve | Medium | | |
| 133. Clone Graph | Solution | Solve | Medium | | |
| 144. Binary Tree Preorder Traversal | Solution | Solve | Easy | | |
| 145. Binary Tree Postorder Traversal | Solution | Solve | Easy | | |
| 156. Binary Tree Upside Down | Solution | Solve | Medium | | |
| 199. Binary Tree Right Side View | Solution | Solve | Medium | | |
| 200. Number of Islands | Solution | Solve | Medium | | |
| 207. Course Schedule | Solution | Solve | Medium | | |
| 210. Course Schedule II | Solution | Solve | Medium | | |
| 211. Design Add and Search Words Data Structure | Solution | Solve | Medium | | |
| 226. Invert Binary Tree | Solution | Solve | Easy | | |
| 230. Kth Smallest Element in a BST | Solution | Solve | Medium | | |
| 235. Lowest Common Ancestor of a Binary Search Tree | Solution | Solve | Medium | | |
| 236. Lowest Common Ancestor of a Binary Tree | Solution | Solve | Medium | | |
| 250. Count Univalue Subtrees | Solution | Solve | Medium | | |
| 257. Binary Tree Paths | Solution | Solve | Easy | | |
| 261. Graph Valid Tree | Solution | Solve | Medium | | |
| 269. Alien Dictionary | Solution | Solve | Hard | | |
| 270. Closest Binary Search Tree Value | Solution | Solve | Easy | | |
| 272. Closest Binary Search Tree Value II | Solution | Solve | Hard | | |
| 285. Inorder Successor in BST | Solution | Solve | Medium | | |
| 297. Serialize and Deserialize Binary Tree | Solution | Solve | Hard | | |
| 298. Binary Tree Longest Consecutive Sequence | Solution | Solve | Medium | | |
| 302. Smallest Rectangle Enclosing Black Pixels | Solution | Solve | Hard | | |
| 310. Minimum Height Trees | Solution | Solve | Medium | | |
| 314. Binary Tree Vertical Order Traversal | Solution | Solve | Medium | | |
| 323. Number of Connected Components in an Undirected Graph | Solution | Solve | Medium | | |
| 329. Longest Increasing Path in a Matrix | Solution | Solve | Hard | | |
| 332. Reconstruct Itinerary | Solution | Solve | Hard | | |
| 333. Largest BST Subtree | Solution | Solve | Medium | | |
| 337. House Robber III | Solution | Solve | Medium | | |
| 339. Nested List Weight Sum | Solution | Solve | Medium | | |
| 341. Flatten Nested List Iterator | Solution | Solve | Medium | | |
| 364. Nested List Weight Sum II | Solution | Solve | Medium | | |
| 365. Water and Jug Problem | Solution | Solve | Medium | | |
