LeetCode 111 Minimum Depth of Binary Tree（DFS）

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.

题目大意：给出一个二叉树，求从根节点到叶节点的最小深度。

解题思路：直接DFS，和LeetCode 104 Maximum Depth of Bianry Tree类似，只不过多了些判断。

代码如下：

/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* struct TreeNode *left;
* struct TreeNode *right;
* };
*/

int minDepth(struct TreeNode* root) {
if(root == NULL) return 0;
else if(root->left && !root->right) return 1 + minDepth(root->left);
else if(root->right && !root->left) return 1 + minDepth(root->right);
else{
int left = 1 + minDepth(root->left);
int right = 1 + minDepth(root->right);
return left < right ? left : right;
}
}