题目描述：
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.
解题思路：
递归。
代码描述：
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int minDepth(TreeNode root) {
if(root == null) return 0;
if(root.left == null) return 1 + minDepth(root.right);
if(root.right == null) return 1 + minDepth(root.left);
return Math.min(1 + minDepth(root.left), 1 + minDepth(root.right));
}
}
Java [Leetcode 111]Minimum Depth of Binary Tree
原文：http://www.cnblogs.com/zihaowang/p/5181354.html