using System;

using System.Collections.Generic;

​

public class Program {

  static bool isBalanced;

​

  public static void Main() {

    int ? [] data = { 3, 9, 20, null, null, 15, 7 };

    BinaryTree aBinaryTree = new BinaryTree(data);

    //aBinaryTree.Add(data);

​

    //aBinaryTree.Add(null);

​

    //aBinaryTree.Add(1);

    //aBinaryTree.Add(2);

    //aBinaryTree.Add(2);

    //aBinaryTree.Add(3);

    //aBinaryTree.Add(3);

    //aBinaryTree.Add(null);

    //aBinaryTree.Add(null);

    //aBinaryTree.Add(4);

    //aBinaryTree.Add(4);

​

    bool status = IsBalanced(aBinaryTree);

​

    Console.WriteLine(status);

  }

​

  static bool IsBalanced(BinaryTree root) {

    isBalanced = true;

​

    int chk = CheckBalance(root.Root, 0);

​

    return isBalanced;

  }

​

  static int CheckBalance(TreeNode root, int depth) {

    if (root == null)

      return depth;

​

    int left = CheckBalance(root.left, depth + 1);

    int right = CheckBalance(root.right, depth + 1);

​

    if (Math.Abs(left - right) > 1)

      isBalanced = false;

    return GetMax(left, right);

  }

​

  static int GetMax(int left, int right) {

    if (left > right)

      return left;

    else

      return right;

  }

}

​

public class TreeNode {

  public int ? val;

  public TreeNode left;

  public TreeNode right;

​

  public TreeNode(int ? val = 0, TreeNode left = null, TreeNode right = null) {

    this.val = val;

    this.left = left;

    this.right = right;

  }

}

​

class BinaryTree {

  public TreeNode Root;

​

  public BinaryTree(int ? [] data) {

    if (data.Length == 0) return;

​

    var queue = new Queue < TreeNode > ();

    Root = new TreeNode(data[0]);

    queue.Enqueue(Root);

​

    for (int i = 1; i < data.Length; i++) {

      TreeNode presentNode = queue.Dequeue();

      if (data[i] != null) {

        presentNode.left = new TreeNode(data[i]);

        queue.Enqueue(presentNode.left);

      }

      i++;

      if (i >= data.Length) break;

      if (data[i] != null) {

        presentNode.right = new TreeNode(data[i]);

        queue.Enqueue(presentNode.right);

      }

    }

  }

}