void printLevel(Node* root) {
    if (!root) return; 

    queue<Node*> q;
    q.push(root);

    while (!q.empty()) {
        Node* node = q.front();
        q.pop();

        cout << node->data << " ";

        if (node->left)  q.push(node->left);
        if (node->right) q.push(node->right);
    }
}