#include<iostream>
#include<queue>
using namespace std;

/*
 * These are simple comparision objects
 * If something uses a type for comparision
 * it only looks for the operator binary ()
 * which is basically a operator < definition
 *
 * priority queues use a high to low order by default
 */
template < class T >
class Normal
{
    public:
        bool operator () ( const T & l, const T & r ) const
        {
            return ( l < r );
        }
};

template < class T >
class Reverse
{
    public:
        bool operator () ( const T & l, const T & r ) const
        {
            return ( r < l );
        }
};


int main()
{
    {
        cout << "normal order heap" << endl;
        // these all pop the high value
        //priority_queue<int> q;
        //priority_queue<int, vector<int>, less<int> > q;
        //priority_queue<int, vector<int>, Normal<int> > q;
        priority_queue<int> q;

        q.push( 42 );
        q.push( 17 );
        q.push( 6 );
        q.push( 91 );

        cout << q.top() << endl;
        q.pop();
        cout << q.top() << endl;
        q.pop();
        cout << q.top() << endl;
        q.pop();
    }
    {
        cout << "reverse order heap" << endl;
        // these all pop the low value
        //priority_queue<int, vector<int>, greater<int> > q;
        //priority_queue<int, vector<int>, Reverse<int> > q;
        priority_queue<int, vector<int>, Reverse<int> > q;

        q.push( 42 );
        q.push( 17 );
        q.push( 6 );
        q.push( 91 );

        cout << q.top() << endl;
        q.pop();
        cout << q.top() << endl;
        q.pop();
        cout << q.top() << endl;
        q.pop();
    }

    return 0;
}