leetcode 111

111. 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.

寻找二叉树的最小深度：递归解法，返回深度最小子树的深度。

代码如下：

 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)
14         {
15             return 0;
16         }
17         if(root->left == NULL && root->right == NULL)
18         {
19             return 1;
20         }
21         else if(root->left == NULL)
22         {
23             return 1 + minDepth(root->right);
24         }
25         else if(root->right == NULL)
26         {
27             return 1 + minDepth(root->left);
28         }
29         else
30         {
31             int l = 1 + minDepth(root->left);
32             int r = 1 + minDepth(root->right);
33             return l > r ? r : l;
34         }
35     }
36 };