LeetCode Maximum Depth of Binary Tree

/**

 * Definition for binary tree

 * 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 (root == NULL) {

            return 0;

        }

        int dl = maxDepth(root->left);

        int dr = maxDepth(root->right);

        return max(dl, dr) + 1;

    }

};

不能更水