练习39

#include <iostream>
using namespace std;


class Shape
{
public:
    Shape(){}
    ~Shape(){}
    virtual float getArea() { return -1; } 
};


class Circle : public Shape
{
public:
    Circle(float radius):itsRadius(radius){}
    ~Circle(){}
    float getArea() { return 3.14 * itsRadius * itsRadius; }
private:
    float itsRadius;
};


class Rectangle : public Shape
{
public:
    Rectangle(float len, float width): itsLength(len), itsWidth(width){};
    ~Rectangle(){};
    virtual float getArea() { return itsLength * itsWidth; }
    virtual float getLength() { return itsLength; }
    virtual float getWidth() { return itsWidth; }
private:
    float itsWidth;
    float itsLength;
};


class Square : public Rectangle
{
public:
       Square(float len);
       ~Square(){}
};


Square::Square(float len):
    Rectangle(len, len)
{
}


int main()
{
    Shape * sp;


sp = new Circle(5);
cout << "The area of the Circle is " << sp->getArea () << endl;
delete sp;
sp = new Rectangle(4, 6);
cout << "The area of the Rectangle is " << sp->getArea() << endl;
delete sp;
sp = new Square(5);
cout << "The area of the Square is " << sp->getArea() << endl;
delete sp;
return 0;
}