Tree top view problem

#1

how to build a binary tree from level order, i made it but it need extra input as ‘‘n’’

#2

you can do it without storing elements in array
like this

node* BuildTree() {
    int d;
    cin >> d;
    if (d == -1)return NULL;
    node* root = new node(d);
    queue<node*>q;
    q.push(root);
    while (!q.empty()) {
        node* temp = q.front();
        q.pop();
        int lc, rc;
        cin >> lc >> rc;
        if (lc != -1) {
            temp->left = new node(lc);
            q.push(temp->left);
        }
        if (rc != -1) {
            temp->right = new node(rc);
            q.push(temp->right);
        }
    }
    return root;
}
#3

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