#include <iostream>

using namespace std;

class Circle;
class Polygon;

class Shape {
public:
  virtual void intersect(Shape *that);
  virtual void intersect(Circle *that)=0;
  virtual void intersect(Polygon *that)=0;
};


class Polygon : public Shape {
public:
  virtual void intersect(Circle *that) {
    cout << "Intersect polygon with circle" << endl;
  }
  virtual void intersect(Polygon *that) {
    cout << "Intersect polygon with polygon" << endl;
  }
 };

class Circle : public Shape {
public:
  virtual void intersect(Circle *that) {
    cout << "Intersect circle with circle" << endl;
  }
  virtual void intersect(Polygon *that) {
    cout << "Intersect circle with polygon" << endl;
  }
};

void Shape::intersect(Shape *that) {
  cout << "(Determining type of second shape)" << endl;
  if (dynamic_cast<Circle*>(that))
    intersect(dynamic_cast<Circle*>(that));
  else if (dynamic_cast<Polygon*>(that))
    intersect(dynamic_cast<Polygon*>(that));
  else
    cout << "Not sure about this, sorry!" << endl;
}

int main()
{
  Shape *shape1 = new Polygon();
  Shape *shape2 = new Circle();
  shape1->intersect(shape2);
}