leetcode------Balanced Binary Tree

标题：	Balanced Binary Tree
通过率：	32.3%
难度：	简单

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.

平衡二叉树。这个可以由二叉树深度来计算，再二叉树深度计算中每次进行深度比较取深度较深的一个，那么平衡二叉树再比较深度时就是A-B绝对值超过一的话就不是二叉树了。立马返回-1 ，当左右子树有一边深度值是-1时立马终止，返回此树非平衡二叉树，如果A-B绝对值总是在0，1，-1三个数之中，那么继续深度递归判断，具体代码如下：

 1 /**

 2  * Definition for binary tree

 3  * public class TreeNode {

 4  *     int val;

 5  *     TreeNode left;

 6  *     TreeNode right;

 7  *     TreeNode(int x) { val = x; }

 8  * }

 9  */

10 public class Solution {

11     public boolean isBalanced(TreeNode root) {

12         if(root==null) return true;

13         if(height(root)==-1) return false;

14         else return true;

15         

16     }

17     public int height(TreeNode root){

18         if(root==null) return 0;

19         int depth1=0;

20         int depth2=0;

21         depth1=height(root.right);

22         depth2=height(root.left);

23         if(depth1==-1||depth2==-1) return -1;

24         if((depth1-depth2>1 )||(depth1-depth2)<-1)

25             return -1;

26         else{

27              if(depth1>depth2)

28             return depth1+1;

29             else

30                 return depth2+1;

31         }

32             

33     }

34 }