Comparators in STL

Question

I am using struct minHeap to generate a min heap using priority_queue .And function comp to print numbers in reverse order using sort function given in STL . Now my doubt is tha

Answer 1

You can use a functor in sort(), no problem at all:

sort(arr , arr+4  ,minHeap());

Maybe your problem was that you were just using the class name (minHeap) instead of an instance of the functor. minHeap() is a call to the constructor, not to operator().

As for priority_queue, it is specified as follows:

template < class T, class Container = vector,
           class Compare = less > class priority_queue;

Therefore, you need a class name (as opposed to an instance) for the third template argument. If you want to use a function, you must use a pointer to a function type as third template argument and then pass the function pointer in the constructor:

priority_queue , bool (*)(int a, int b) > b(&comp);