class BinarySearchTree {
  final TreeNode root;
  List<String> get sortedData => _traverseInOrder(this.root);

  BinarySearchTree(String rootValue) : root = TreeNode(rootValue);

  void insert(String value) {
    TreeNode newTreeNode = TreeNode(value);
    TreeNode currentValue = root;

    while (true) {
      if (int.parse(value) <= int.parse(currentValue.data)) {
        if (currentValue.left == null) {
          currentValue.left = newTreeNode;
          break;
        }
        currentValue = currentValue.left!;
      } else {
        if (currentValue.right == null) {
          currentValue.right = newTreeNode;
          break;
        }
        currentValue = currentValue.right!;
      }
    }
  }

  List<String> _traverseInOrder(TreeNode? node) {
    List<String> data = [];
    if (node != null) {
      data.addAll(_traverseInOrder(node.left));
      data.add(node.data);
      data.addAll(_traverseInOrder(node.right));
    }
    return data;
  }
}

class TreeNode {
  String data;
  TreeNode? left;
  TreeNode? right;

  TreeNode(this.data);
}