知识点
找最接近的数：BST左右间隔的范围缩窄
- Closest Binary Search Tree Value II — https://www.lintcode.com/problem/901/?_from=collection&fromId=161
追踪最大/最小值
- max(left, right) + 1 来追踪最长路径
Maximum Depth of Binary Tree — https://www.lintcode.com/problem/97/description?_from=collection&fromId=161
通过返回多个变量来判断条件
- Validate binary search tree — https://www.lintcode.com/problem/95/?_from=collection&fromId=161
- Balanced Binary Tree — https://www.lintcode.com/problem/93/?_from=collection&fromId=161
- Lowest Common Ancestor III — https://www.lintcode.com/submission/27303984/?action_type=1
插入/删除新节点
