void topView(Node* root) {
    std::queue<std::pair<int, Node*>> q;
    q.push(std::make_pair(0,root));

    while (!q.empty())
    {
        auto i = q.front();
        if(i.second != nullptr)
        {
            q.push(std::make_pair(i.first-1, i.second -> left));
            q.push(std::make_pair(i.first+1, i.second -> right));
            std::cout<<i.second->data<<' ';    
        }
        q.pop();
        i=q.front();

    }

    
}