priority_queue

algorithm

// constructing priority queues
#include <iostream>       // std::cout
#include <queue>          // std::priority_queue
#include <vector>         // std::vector
#include <functional>     // std::greater
using namespace std;
class mycomparison {
    bool reverse;
public:
    mycomparison(const bool &revparam = false)
    { reverse = revparam; }
    bool operator()(const int &lhs, const int &rhs) const
    {
        if (reverse) return (lhs > rhs);
        else return (lhs < rhs);
    }
};
template <typename T>
void PrintQueue(T& q)
{
    while (!q.empty())
    {
        cout << q.top()<< " ";
        q.pop();
    }
    cout << "\n";
}
int main()
{
    int myints[] = {10, 60, 50, 20};
    std::priority_queue<int> second(myints, myints + 4);
    std::priority_queue<int, std::vector<int>, std::greater<int> > third(myints, myints + 4);
    // using mycomparison:
    typedef std::priority_queue<int, std::vector<int>, mycomparison> mypq_type;
    mypq_type fifth(mycomparison(true));   // greater-than comparison
    PrintQueue(second);
    PrintQueue(third);
    PrintQueue(fifth);
    return 0;
}

output:

60 50 20 10 
10 20 50 60