110. Balanced Binary Tree Java Solutions

 1 /**
 2  * Definition for a binary tree node.
 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         return height(root) != -1;
13     }
14     
15     public int height(TreeNode t){
16         if(t == null) return 0; //到叶子节点再往下的情况
17         int lheight = height(t.left);
18         int rheight = height(t.right);
19         if(lheight == -1 || rheight == -1 || Math.abs(lheight-rheight) > 1){
20             return -1;//使用-1 标记左右子树高度相差大于1的情况
21         }
22         return 1 + Math.max(lheight,rheight);
23     }
24 }