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.

一开始的考虑很有问题，忘了考虑是到结点（左右子树都为空）的路径，所以就有了下面的代码：

/** * 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;        return Math.min(minDepth(root.left),minDepth(root.right))+1;    }}

很显然，以上代码如果跑

       2

1

得到的结果是1；

但是实际上应该是为2.。

修正后代码如下：添加了左子树为空，和 右子树为空的情况。

/** * 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 minDepth(root.right)+1;        if(root.right ==null) return minDepth(root.left)+1;        return Math.min(minDepth(root.left),minDepth(root.right))+1;    }}