#include <queue>
#include <vector>
#include <iostream>
using namespace std; // make std accessible

class Point2D{
   public:
	Point2D(float x, float y):X_(x),Y_(y){}
  	float getX() const {return X_;}
	float getY() const {return Y_;}
	friend ostream &operator<<( ostream &output, const Point2D& p){output << "(" << p.X_ << "," << p.Y_ << ")"; return output;}
   private:
	float X_, Y_;
};

class LeftRight { // a left-right comparator
public:
	bool operator()(const Point2D& p, const Point2D& q) const
	{ return p.getX() < q.getX(); }
};

class BottomTop { // a bottom-top comparator
public:
	bool operator()(const Point2D& p, const Point2D& q) const
	{ return p.getY() < q.getY(); }
};


template <typename E, typename C> // element type and comparator
void printSmaller(const E& p, const E& q, const C& isLess) {
	cout << (isLess(p, q) ? p : q) << endl; // print the smaller of p and q
}




int main(){
	priority_queue<int> p1; // a priority queue of integers
	p1.push(5);
	p1.push(3);
	p1.push(7);
	cout << p1.top() << endl; p1.pop();
	cout << p1.top() << endl; p1.pop();
	cout << p1.top() << endl; p1.pop();	

	// a priority queue of points with left-to-right order
	priority_queue<Point2D, vector<Point2D>, LeftRight> p2;
	p2.push( Point2D(8.5, 4.6) ); // add three points to p2
	p2.push( Point2D(1.3, 5.7) );
	p2.push( Point2D(2.5, 0.6) );
	cout << p2.top() << endl; p2.pop(); // output: (8.5, 4.6)
	cout << p2.top() << endl; p2.pop(); // output: (2.5, 0.6)
	cout << p2.top() << endl; p2.pop(); // output: (1.3, 5.7)

	Point2D p(1.3, 5.7), q(2.5, 0.6); // two points
	LeftRight leftRight; // a left-right comparator
	BottomTop bottomTop; // a bottom-top comparator
	printSmaller(p, q, leftRight); // outputs: (1.3, 5.7)
	printSmaller(p, q, bottomTop); // outputs: (2.5, 0.6)
	
	return 0;
}