Why does this use of std::sort with a custom comparator not compile?

Question

I trying to use sort algorithm for sorting the elements of a vector. This is my code snippet.

Comparator

struct comparator
 {
    boo         


        

Answer 1

The comparator functor is supposed to take the elements but not the iterators as the parameter for comparing.

You should change the parameter type of comparator::operator() from iterator to value type:

struct comparator
{
    bool operator() ( const pair > & lhs, const pair > & rhs) const
    {
        return lhs.first < rhs.first;
    }
};

^{BTW: Making operator() const member function is a good habit.}