LeetCode Minimum Depth of Binary Tree

Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

简单的考研题，求个最小深度嘛

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