Balanced Binary Tree

 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     /**
12      * 这里用递归实现
13      * 如果为空节点返回true
14      * 如果不为空比较左右子树的高度，如果高度差的绝对值小于等于1且左右子树都是平衡二叉树return true
15      * @param root
16      * @return
17      */
18     public boolean isBalanced(TreeNode root){
19         if(null == root){
20             return true;
21         }else
22         {
23             return (Math.abs(getHeight(root.left) - getHeight(root.right)) <= 1) && isBalanced(root.left) && isBalanced(root.right);
24         }
25         
26     }
27     /**
28      * 获取一棵树的高度
29      * 递归获取
30      * @param root
31      * @return
32      */
33     public int getHeight(TreeNode root){
34         if(null == root)
35             return 0;
36         else{
37             int max = getHeight(root.left);
38             if(max < getHeight(root.right))
39             {
40                 max =getHeight(root.right);
41             }
42             return max + 1;
43         }
44     }
45 }