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.

思路：Using  recursion to solve this problem.

易错点： 必须是叶子节点才能返回1， left  和 right 初始化必须为 Integer.MAX_VALUE , 防止出现单边不是叶子节点的情况。

/** * Definition for binary tree * 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 && root.right == null)            return 1;        int left = Integer.MAX_VALUE, right = Integer.MAX_VALUE;        if(root.left != null)            left = minDepth(root.left);        if(root.right != null)            right = minDepth(root.right);        return Math.min(left, right) + 1;    }}