Maximum Depth of Binary Tree

/**
* 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 (root==NULL)
return 0;
else
{
int ml=maxDepth(root->left);
int mr=maxDepth(root->right);
if (ml>mr)
return ++ml;
else
return ++mr;
}
}
};