int getHeight(TreeNode *root)

      {

          if (root == nullptr)return ;

          return max(getHeight(root->left), getHeight(root->right)) + ;

      }

      bool isBalancedTree(TreeNode *root)

      {

          if (root == nullptr)return true;

          if (root->left == nullptr && root->right == nullptr)return true;

          if (abs(getHeight(root->left) - getHeight(root->right)) > )return false;

          return(isBalancedTree(root->left) && isBalancedTree(root->right));

      }