LeetCode --- Maximum Depth of Binary Tree

求树的最大深度

附上代码：

 1 /**
 2  * Definition for binary tree
 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 == NULL && root->right == NULL) return 1;
15         int ans = 1;
16         if (root->left != NULL) ans = maxDepth(root->left) + 1;
17         if (root->right != NULL) ans = max(ans, maxDepth(root->right)+1);
18         
19         return ans;
20     }
21 };