[leetcode 111]Minimum Depth of Binary Tree

Question:

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.
分析：
1、root = NULL，深度为0；

2、root没有左右子树的时候深度为1；

3、左右子树最小深度加1；

代码：

<span style="font-size:14px;">/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
int minDepth(TreeNode* root) {
if(root == NULL)
return 0;
int l  = INT_MAX,r = INT_MAX;
if(root->left== NULL && root->right == NULL)
return 1;
else{
if(root->left != NULL)
l = minDepth(root->left);
if(root->right != NULL)
r = minDepth(root->right);
}
return min(l,r)+1;
}
};</span>