Comparator for min-heap in C++

Question

I am trying to make a min-heap¹ of longs in C++ using the STL make_heap, etc., but my comparator doesn\'t seem to be comparing properly. The

Answer 1

You want to call make_heap on the vector again, not sort_heap. make_heap will rearrange your entire vector into a min heap given the greater-than comparator whereas sort_heap sorts your element into ascending order and is no longer a heap at all!

#include 
#include 
#include 

struct greater1{
    bool operator()(const long& a,const long& b) const{
        return a>b;
    }
};

int main()
{
  unsigned int myints[] = {10,20,30,5,15};
  vector v(myints, myints+5);

  //creates max heap
  std::make_heap(v.begin(). v.end()); // 30 20 10 5 15

  //converts to min heap
  std::make_heap(v.begin(). v.end(), greater1()); // 5 15 10 20 30

  unsigned int s =  v.size();

  //ALSO NEED TO PASS greater1() to pop()!!!
  for(unsigned int i = 0; i < s; i++)
    std::pop_heap(v.begin(). v.end(), greater1()); // popping order: 5 10 15 20 30

  return 0;
}