111. 二叉树的最小深度

 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 {
12 public:
13     int minDepth(TreeNode* root) 
14     {
15         if(!root) return 0;
16         if(root->left == NULL) return minDepth(root->right) + 1;
17         else if(root->right == NULL) return minDepth(root->left) + 1;
18         else return min(minDepth(root->left),minDepth(root->right)) + 1;
19     }
20 };