/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public boolean isBalanced(TreeNode root) {
      if(root == null) return true;
      
      if(Math.abs(getHeight(root.left) - getHeight(root.right)) > 1)
        return false;
      return isBalanced(root.left) && isBalanced(root.right);
    }
    
    
    public int getHeight(TreeNode root){
        if(root == null)
            return 0;
        return Math.max(getHeight(root.left), getHeight(root.right))+1; // Attention +1
         
    }
}