Balanced Binary Tree

Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as:

a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

Example 1:

Given the following tree [3,9,20,null,null,15,7]:

    3
   / \
  9  20
    /  \
   15   7

Return true. Example 2:

Given the following tree [1,2,2,3,3,null,null,4,4]:

       1
      / \
     2   2
    / \
   3   3
  / \
 4   4

Return false.

time o(n), space o(h), height of the tree

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */

class Type{
    int height;
    int diff;
    boolean flag;
    public Type(int h, int d,boolean f){
        this.height = h;
        this.diff = d;
        this.flag = f;
    }
}

class Solution {
    
    public boolean isBalanced(TreeNode root) {
        if(root == null) return true;
        
        Type res = help(root);
        
        return res.flag;
    }
    
    public Type help(TreeNode root){
        if(root == null) return new Type(0,0,true);
        
        Type left = help(root.left);
        Type right = help(root.right);
        
        int diff = Math.abs(left.height - right.height);
        
        boolean flag = false;
        
        if(diff <= 1 && left.flag == true && right.flag == true) flag = true;
        
       
        int height = Math.max(left.height, right.height) + 1;
        
        return new Type(height,diff,flag);
    }
    
  
}