面试题55 - I. 二叉树的深度

题目：

 

 

解答：

/**
 * 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 maxDepth(TreeNode* root) 
    {
        if (NULL == root)
        {
            return 0;
        }

        int leftdepth = maxDepth(root->left);
        int rightdepth = maxDepth(root->right);
        
        return std::max(leftdepth, rightdepth) + 1;

    }
};