[leetcode]543. Diameter of Binary Tree[facebook]

Given a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.

Example:
Given a binary tree 

          1         / \        2   3       / \           4   5    

Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3].

Note: The length of path between two nodes is represented by the number of edges between them.

我的做法：

首先，树的问题我都不会，需要严重沉痛反思！

然后，没有解题思路..

solution是说，经过这一个点的最长path应该是它的左path的depth加上它的右path的depth－1。

依然用了递归。

递归依然是我的死穴。。。