形状类族中的纯虚函数

#include "iostream"
using namespace std;

const double pai=3.14159;

class CSolid
{
public:
virtual double SurfaceArea() const=0;
virtual double Volume() const=0;
};

class CCube : public CSolid
{
public:
CCube(double len=0);
double SurfaceArea() const;
double Volume() const;
private:
double length;

};

CCube::CCube(double len)
{
length=len;
}

double CCube::SurfaceArea() const
{
double c;
c=6*length*length;
return c;
}

double CCube::Volume() const
{
double c;
c=length*length*length;
return c;
}

class CBall : public CSolid
{
private:
double radius;
public:
CBall(double r=0);
double SurfaceArea() const;
double Volume() const;
};
CBall::CBall(double r)
{
radius=r;
}

double CBall::SurfaceArea() const
{
double c;
c=4*pai*radius*radius;
return c;
}

double CBall::Volume() const
{
double c;
c=pai*radius*radius*radius*4/3;
return c;
}

class CCylinder : public CSolid
{
private:
double radius;
double height;
public:
CCylinder(double r=0,double high=0);
double SurfaceArea() const;
double Volume() const;
};
CCylinder::CCylinder(double r,double high)
{
radius=r;
height=high;
}
double CCylinder::SurfaceArea() const
{
double c;
c=2*pai*radius*radius+2*pai*radius*height;
return c;
}
double CCylinder::Volume() const
{
double c;
c=pai*radius*radius*height;
return c;
}

int main( )
{
CSolid *p;
double s,v;
CCube x(30);
cout<<"立方体边长为 30 "<<endl;
p=&x;
s=p->SurfaceArea( );
v=p->Volume( );
cout<<"表面积："<<s<<endl;
cout<<"体积："<<v<<endl;
cout<<endl;
CBall y(4.5);
cout<<"球体半径为 4.5 "<<endl;
p=&y;
s=p->SurfaceArea( );
v=p->Volume( );
cout<<"表面积："<<s<<endl;
cout<<"体积："<<v<<endl;
cout<<endl;
CCylinder z(10,20);
cout<<"圆柱体底面半径、高分别为 10, 20"<<endl;
p=&z;
s=p->SurfaceArea( );
v=p->Volume( );
cout<<"表面积："<<s<<endl;
cout<<"体积："<<v<<endl;
cout<<endl;
return 0;
}