543. Diameter of Binary Tree

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.

这道题和上一道题是差不多的，都是递归，先是每一步算出每个左右子树的深度，然后再每一步中都要计算最终的值，不断更新最终的值。
代码如下：

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    int maxx=0;    int diameterOfBinaryTree(TreeNode* root) {        depth(root);        return maxx;    }    int depth(TreeNode* root)    {        if(root==NULL)return 0;        int left=depth(root->left);        int right=depth(root->right);        maxx=max(maxx,left+right);        return max(left,right)+1;    }};