第六单元

1. #include <iostream.h>  

class Point  

{public:  

    Point(float x=0,float y=0);  

    void setPoint(float,float);  

    float getX() const  

    {return x;}  

    float getY() const  

    {return y;}  

    friend ostream & operator<<(ostream &output,Point &);  

protected:  

    float x,y;  

};  

Point::Point(float a,float b)  

{  

    x=a;y=b;  

}  

void Point::setPoint(float a,float b)  

{  

 x=a;y=b;  

}  

ostream & operator<<(ostream &output,Point &p)  

{  

 output<<"["<<p.x<<","<<p.y<<"]"<<endl;  

 return output;  

}  

class Circle:public Point  

{  

public:  

    Circle(float x,float y,float r):Point(x,y),radius(r){}  

    void setRadius(float r)  

    {radius=r;}  

    float getRadius() const  

    {return radius;}  

    double area() const  

    {  

     return 3.1415*radius*radius;  

    }  

    friend ostream & operator<<(ostream &output,Circle &);  

protected:  

    float radius;  

};  

ostream & operator<<(ostream &output,Circle &c)  

{  

    output<<"Center =["<<c.x<<","<<c.y<<"],r= "<<c.radius<<",area="<<c.area()<<endl;  

    return output;  

}  

class Cylinder:public Circle  

{  

public:  

    Cylinder(float x,float y,float r,float h):Circle(x,y,r),height(h){}  

    void setHeight(float h)  

    {height=h;}  

    float getHeight() const  

    {return height;}  

    double area() const  

    {  

        return 2*Circle::area()+2*3.1415*radius*height;   

    }  

    double volume() const  

    {  

        return 3.1415*radius*radius*height;  

    }  

    friend ostream & operator<<(ostream &output,Cylinder &);  

protected:  

    float height;  

};  

ostream & operator<<(ostream &output,Cylinder &cy)  

{  

 output<<"Center=["<<cy.x<<cy.y<<"],r="<<cy.radius<<",h="<<cy.height<<"\narea="<<cy.area()<<",volume="<<cy.volume()<<endl;  

 return output;  

}  

int main()  

{  

 Cylinder cy1(3.5,6.4,5.2,10);  

 cout<<"original cylinder:\nx="<<cy1.getX()<<",y="<<cy1.getY()<<",r="<<cy1.getRadius()<<",h="<<cy1.getHeight()<<"\narea="<<cy1.area()<<",volume="<<cy1.volume()<<endl;  

 cy1.setHeight(15);  

 cy1.setRadius(7.5);  

 cy1.setPoint(5,5);  

 cout<<"\nnew cylinder:\n"<<cy1;  

 Point &pRef=cy1;  

 cout<<"\npRef as a point:"<<pRef;  

 Circle &cRef=cy1;  

 cout<<"\ncRef as a circle:"<<cRef;  

 return 0;  
} 

 3.(1) #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(1,2,3);  

 delete p;  

 return 0;  

}  

(3) #include <iostream>  

using namespace std;  

class Point  

{  

 public:  

     Point(float a,float b):x(a),y(b){}  

     virtual ~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(1,2,3);  

 delete p;  

 return 0;  

}  

4. #include <iostream.h>  

class Shape{  

public:  

    virtual double area()const =0;  

};  

class Circle:public Shape  

{  

public:  

    Circle(double r):radius(r){}  

    virtual double area() const  

    {  

     return 3.1415*radius*radius;  

    }  

protected:  

    double radius;  

};  

class Rectangle :public Shape{  

public:  

    Rectangle(double l,double w):length(l),width(w){}  

    virtual double area()const  

    {  

     return length*width;  

    }  

protected:  

    double length;  

    double width;  

};  

class Triangle:public Shape  

{  

public:  

    Triangle(double d,double h):dibian(d),height(h){}  

    virtual double area() const  

    {  

     return 0.5*dibian*height;  

    }  

protected:  

    double dibian;  

    double height;  

};  

void display(const Shape &s)  

{  

 cout<<s.area()<<endl;  

}  

int main()  

{  

 Circle c(4);  

 cout<<"area of c is ";  

 display(c);  

 Rectangle r(2,4);  

 cout<<"area of r is ";  

 display(r);  

 Triangle t(1,2);  

 cout<<"area of t is ";  

 display(t);  

 return 0;  

}  

5. #include <iostream.h>  

class Shape{  

public:  

    virtual double area()const =0;  

};  

class Circle:public Shape  

{  

public:  

    Circle(double r):radius(r){}  

    virtual double area() const  

    {  

     return 3.1415*radius*radius;  

    }  

protected:  

    double radius;  

};  

class Rectangle :public Shape{  

public:  

    Rectangle(double l,double w):length(l),width(w){}  

    virtual double area()const  

    {  

     return length*width;  

    }  

protected:  

    double length;  

    double width;  

};  

class Triangle:public Shape  

{  

public:  

    Triangle(double d,double h):dibian(d),height(h){}  

    virtual double area() const  

    {  

     return 0.5*dibian*height;  

    }  

protected:  

    double dibian;  

    double height;  

};  

class Square:public Shape{  

public:  

    Square(double s):side(s){}  

    virtual double area() const  

    {  

     return side*side;  

    }  

protected:  

    double side;  

};  

class Trapezoid:public Shape  

{  

public:  

    Trapezoid(double t,double b,double h):top(t),bottem(b),height(h){}  

    virtual double area() const  

    {  

     return 0.5*(top+bottem)*height;  

    }  

protected:  

    double top,bottem,height;  

};  

void display(const Shape &s)  

{  

 cout<<s.area()<<endl;  

}  

int main()  

{  

 Circle c(4);  

 Rectangle r(2,4);  

 Triangle t(1,2);  

 Square s(2);  

 Trapezoid tt(1,2,3);  

 Shape *p[5]={&c,&r,&t,&s,&tt};  

 double area=0.0;  

 for(int i=0;i<5;i++)  

 {  

  area=area+p[i]->area();  

 }  

 cout<<"the sum of area is "<<area<<endl;  

 return 0;  

}