#include <vector>
#include <algorithm>
struct doc {
double rank;
explicit doc(double r) : rank(r) {}
};
struct doc_rank_greater_than {
bool operator()(doc const& a, doc const& b) const {
return a.rank > b.rank;
}
};
int main() {
std::vector<doc> docvec;
docvec.push_back( doc(4) );
docvec.push_back( doc(3) );
docvec.push_back( doc(2) );
docvec.push_back( doc(1) );
std::make_heap(docvec.begin(),docvec.end(),doc_rank_greater_than());
std::cout << docvec.front().rank << '\n';
}
The above is a code for creating minheap for a user defined data type using custom comparator. why are we using a.rank>b.rank instead of a.rank<b.rank for creating minheap?
As suggested by the documentation of std::make_heap
, the function constructs a max heap by default. Reversing the comparison function makes it construct a min heap instead.
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