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.

 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) {
13         if(root==NULL) return 0;
14         if(!root->left&&!root->right)
15             return 1;
16         int leftDepth=maxDepth(root->left);
17         int rightDepth=maxDepth(root->right);
18         
19         if(leftDepth==0)
20             return rightDepth+1;
21         if(rightDepth==0)
22             return leftDepth+1;
23         else 
24             return max(rightDepth,leftDepth)+1;
25     }
26 };