Exercise about Shape

#include <iostream>
using namespace std;
class point 
{
    int x;
    int y;
public :
    point ()
    {
        x=y=0;
    }
    point (int a,int b)
    {
        x=a;
        y=b;
    }
    ~point (){}
    void show ()
    {
        cout <<"("<<x<<","<<y<<")"<<endl;
    }
};
class Shape
{
private:
    double longth;
    double width;
public :
    Shape ()
    {
        longth=width=0;
    }
    Shape (double l,double w)
    {
        longth=l;
        width=w;
        cout<<"构造函数，创建Shape"<<endl;
    }
    ~Shape()
    {
        cout <<"析构函数，释放Shape"<<endl;
    }
    double area()
    {
        double s;
        s=longth*width;
        return s;
    }
    void show ()
    {
        cout <<"面积="<<area()<<endl;
    }
};
class Rectangle:public Shape
{
public :
    Rectangle():Shape(0,0){}
    Rectangle(double a,double b):Shape(a,b)
    {
        cout<<"创建Rectangle"<<endl;
    }
    void show ()
    {
        cout <<"面积="<<area()<<endl;
    }
    ~Rectangle()
    {
        cout <<"析构函数，释放Rectangle"<<endl;
    }
};
class Square:public Rectangle
{
public :
    Square(double a):Rectangle(a,a)
    {
        cout<<"构造函数，创建Square"<<endl;
    }
    ~Square()
    {
        cout <<"析构函数，释放Square"<<endl;
    }
};
class Circle:public Shape
{
private :
    double r;
    point p;
public :
    Circle(double c,point n):Shape(c,c)
    {
        r=c;
        p=n;
        cout<<"构造函数，创建Circle"<<endl;
    }
    ~Circle()
    {
        cout <<"析构函数，释放Circle"<<endl;
    }
    double area()
    {
        double s;
        s=3.14*r*r;
        return s;
    }
    void show ()
    {
        cout <<"面积="<<area()<<endl;
    }
};
int main()
{
    Rectangle r(2,4);
    r.show();
    point o(1,1);
    Circle c (4.0,o);
    c.show ();
    Square s(4);
    s.show();
    return 0;
}