二叉树 - 子树分解题 #基础 #https://leetcode-cn.com/problems/diameter-of-binary-tree/https://leetcode-cn.com/problems/invert-binary-tree/submissions/ https://leetcode-cn.com/problems/flatten-binary-tree-to-linked-list/构造题 #https://leetcode-cn.com/problems/maximum-binary-tree/