[leetcode]Balanced Binary Tree

 1 public class Solution {
 2    public boolean isBalanced(TreeNode root) {
 3         if(root == null || (root.left == null && root.right == null))
 4             return true;
 5         if(!isBalanced(root.left) || !isBalanced(root.right))
 6             return false;
 7         int left = getHeight(root.left);
 8         int right = getHeight(root.right);
 9         if(Math.abs(right - left) > 1) return false;
10         return true;
11     }
12     
13     private int getHeight(TreeNode root){
14         if(root == null) return 0;
15         if(root.left == null && root.right == null) return 1;
16         int left = 0,right = 0;
17         if(root.left != null) left = getHeight(root.left);
18         if(root.right != null) right = getHeight(root.right);
19         return Math.max(left, right) + 1;
20     }
21 }