LeetCode--Balanced Binary Tree

Problem:

Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as a binary
tree in which the depth of the two subtrees of every node never differ
by more than 1.

Analysis:
题意：
给定的二进制树，确定它是否是均衡二叉树。
对于这个问题，一个高度平衡二叉树被定义为一种二叉树，其中各节点的两个子树的深度相差不能超过1。
Anwser:

public class Solution {
    public boolean isBalanced(TreeNode root) {
        if(root==null) return true;
        //下面两行可以改为return depth(root)!=-1;
        if(depth(root)!=-1) return true;
        else return false;
    }
    public int depth(TreeNode root){
        if(root==null) return 0;
        int ldep,rdep;
        ldep = depth(root.left);
        rdep = depth(root.right);
        //-----这两行是比求树的高度多出的代码，从这里多加一层判断来满足要求。-----//
        if(ldep==-1 || rdep==-1) return -1;
        if(Math.abs(ldep-rdep)>1) return -1;
        //-------------------------------------------------------------//
        else {
            return Math.max(ldep,rdep)+1;
        }
    }

}