LeetCode: Maximum Depth of Binary Tree

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.

 /**  
  * Definition for binary tree  
  * struct TreeNode {  
  *   int val;  
  *   TreeNode *left;  
  *   TreeNode *right;  
  *   TreeNode(int x) : val(x), left(NULL), right(NULL) {}  
  * };  
  */  

   int maxDepth(TreeNode *root) {  
     if(!root)return 0;  
     if(!root->left && !root->right)return 1;  
     int x = maxDepth(root->left);  
     int y = maxDepth(root->right);  
     return (max(x,y)+1);  
   }