Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

 

 递归遍历就好了。

1 /** 2  * Definition for a binary tree node. 3  * struct TreeNode { 4  *     int val; 5  *     TreeNode *left; 6  *     TreeNode *right; 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8  * }; 9  */10 class Solution {11 public:12     int maxDepth(TreeNode* root) {13         if(root==NULL) return 0;14         return max(maxDepth(root->left),maxDepth(root->right))+1;15     }16 };