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) {
13if(root == NULL)
14return0;
1516return1 + max(maxDepth(root->left), maxDepth(root->right));
17    }
18 };