Tree

Tree 的题目基本上是三大套路：

• Recursive DFS

• Iterative DFS

• BFS

简单题

lc110: Balanced Binary Tree

lc102: Binary Tree Level Order Traversal II

lc104: Maximum Depth of Binary Tree

lc111: Minimum Depth of Binary Tree

lc100: Same Tree

lc101: Symmetric Tree

lc96: Unique Binary Search Trees

lc95: Unique Binary Search Trees II

Pre-order, In-order, Post-order traversal

serialization/deserialization

LinkedList 和 Binary Tree 相互转换的题目

lc108: Convert Sorted List to Binary Search Tree

lc114: Flatten Binary Tree to Linked List
(这题原题在CC150是一道双向链表题，不知道Leetcode上怎么改单向了。双向链表应该
更复杂一些，大家要注意一下）