Heapsort without make_heap

heapsort.cpp

void heapsort(std::vector<int>& v)
{
    std::vector<int> u;
    for(auto i : v)
    {
        u.push_back(i);
        std::push_heap(u.begin(), u.end(), std::greater<int>{});
    }
    for(auto& i : v)
    {
        std::pop_heap(u.begin(), u.end(), std::greater<int>{});
        i = u.back();
        u.pop_back();
    }
}