Decart experimental

PTree find(PTree t, int key)
{
    if (!t)
        return NULL;

    if (t -> key == key)
        return t;

    if (key < t -> key)
        return find(t -> l, key);
    else
        return find(t -> r, key);
}

PTree merge(PTree l, PTree r)
{
    if (!l || !r)
        {
            return l ? l : r;
        }

    if (l -> prior > r -> prior)
        return merge(l -> r, r);
    else
        return merge(l, r -> l);
}

void erase(PTree &t, int key)
{
    PTree tmp = find(t, key);

    PTree k = merge(tmp -> l, tmp -> r);

    *&tmp = k;
}