Classical:
110. Balanced Binary Tree
98. Validate Binary Search Tree
Tree Path:
112. Path Sum
113. Path Sum II
129. Sum Root to Leaf Numbers
124. Binary Tree Maximum Path Sum
687. Longest Univalue Path
543. Diameter of Binary Tree
437. Path Sum III Prefix Sum
Tree + Linked List:
426. Convert Binary Search Tree to Sorted Doubly Linked List
Tree Traversal:
94. Binary Tree Inorder Traversal
144. Binary Tree Preorder Traversal
145. Binary Tree Postorder Traversal
102. Binary Tree Level Order Traversal
103. Binary Tree Zigzag Level Order Traversal
199. Binary Tree Right Side View
314. Binary Tree Vertical Order Traversal
Serialization and Deserialization of Tree:
297. Serialize and Deserialize Binary Tree
449. Serialize and Deserialize BST
428. Serialize and Deserialize N-ary Tree
Construct Tree:
105. Construct Binary Tree from Preorder and Inorder Traversal TODO
106. Construct Binary Tree from Inorder and Postorder Traversal TODO
LCA:
235. Lowest Common Ancestor of a Binary Search Tree
236. Lowest Common Ancestor of a Binary Tree
Tree + Binary Search:
270. Closest Binary Search Tree Value
272. Closest Binary Search Tree Value II TODO