第三题

#include <iostream>

using namespace std;

class Point

{public:

  Point(float a,float b):x(a),y(b){}

  ~Point(){cout<<"executing Point destructor"<<endl;}

 private:

  float x;

  float y;

};

class Circle:public Point

{public:

 Circle(float a,float b,float r):Point(a,b),radius(r){}

  ~Circle(){cout<<"executing Circle destructor"<<endl;}

 private:

  float radius;

};

int main()

{Point *p=new Circle(2.5,1.8,4.5);

 delete p;

 return 0;

}