/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    boolean flag = true;
    public boolean isBalanced(TreeNode root) {
        lenth(root);
        return flag;
    }

    public int lenth(TreeNode node){
        if(node == null){
            return 0;
        }
        int l = lenth(node.left);
        int r = lenth(node.right);
        int gap = l - r;
        if(gap < 0){
            gap = 0 - gap;
        }
        if(gap > 1){
            flag = false;
        }
        return l > r? l+1 : r+1;
    }
    
}