C++ 虚函数使用以及继承的问题 ?

Question

C++ 虚函数使用以及继承的问题 

Answer 1

#include <iostream>
#define PI 3.14
using namespace std;
class container
{
public:
container(int radius=0){
this->radius = radius;/*赋值给类的成员变量*/
}
virtual void Square()=0;
virtual void Volume()=0;
int GetRadius(){return radius;} /*给私有成员变量提供一个访问的函数*/
/*要想修改就提供一个void SetRadius(int radius)的函数*/
private:
int radius;
};
class cube:public container
{
public:
cube(int radius1):container(radius1){}
virtual void Square()
{
/*基类的私有成员在这里无法之间反问，可通过基类的成员函数访问，下面凡事访问radius都通过
GetRadius()来访问*/
square1=4*PI*GetRadius()*GetRadius();
cout<<"the cube's square is:"<<square1<<endl;
}
virtual void Volume()
{
volume1=(4.0/3)*PI*GetRadius()*GetRadius()*GetRadius();/*4/3等于1了，要写成4.0/3才对 */
cout<<"the cube's volume is:"<<volume1<<endl; /*这里应该是volume1*/
}
private:
double square1,volume1;
};
class sphere:public container
{
public:
sphere(int radius1):container(radius1){}
virtual void Square()
{
square2=6*GetRadius()*GetRadius();
cout<<"the sphere's square is:"<<square2<<endl;
}
virtual void Volume()
{
volume2=GetRadius()*GetRadius()*GetRadius();
cout<<"the sphere's volume is:"<<volume2<<endl;
}
private:
double square2,volume2;
};
class cylinder:public container
{
public:
cylinder(int radius1):container(radius1){}
virtual void Square()
{
cout<<"please input the cylinder's height=";
cin>>height;
square3=2*PI*GetRadius()*GetRadius()+2*PI*GetRadius()*height;
cout<<"the cylinder's square is:"<<square3<<endl;
}
virtual void Volume()
{
volume3=PI*GetRadius()*GetRadius()*height;
cout<<"the cylinder's volume is:"<<volume3<<endl;
}
private:
double square3,volume3;
int height;
};
int main()
{
//container container1;
int a;
cout<<"Please input a radius=";
cin>>a;
cube cube1(a);
sphere sphere1(a);
cylinder cylinder1(a);
cube1.Volume();
cube1.Square();
sphere1.Volume();
sphere1.Square();
cylinder1.Square();
cylinder1.Volume();
return 0;
}

Answer 2

#include <iostream>
#define PI 3.14
using namespace std;
class container
{
public:
container(int radius=0){}
virtual void Square()=0;
virtual void Volume()=0;
//private: //因为这个是私有的，不能被继承类访问，为了简单，我将它改成了public
int radius;
};
class cube:public container
{
public:
cube(int radius1):container(radius1){} //这里int必须去掉
virtual void Square()
{
square1=4*PI*radius*radius; //////////////////基类的成员是radius，没有1，你写成了radius1
cout<<"the cube's square is:"<<square1<<endl;
}
virtual void Volume()
{
volume1=4/3*PI*radius*radius*radius; //////////////////基类的成员是radius，没有1，你写成了radius1
cout<<"the cube's volume is:"<<square1<<endl;
}
private:
double square1,volume1;
};
class sphere:public container
{
public:
sphere(int radius1):container(radius1){} //这里int必须去掉
virtual void Square()
{
square2=6*radius*radius; //////////////////基类的成员是radius，没有1，你写成了radius1
cout<<"the sphere's square is:"<<square2<<endl;
}
virtual void Volume()
{
volume2=radius*radius*radius; //////////////////基类的成员是radius，没有1，你写成了radius1
cout<<"the sphere's volume is:"<<volume2<<endl;
}
private:
double square2,volume2;
};
class cylinder:public container
{
public:
cylinder(int radius1):container(radius1){} //这里int必须去掉
virtual void Square()
{
cout<<"please input the cylinder's height=";
cin>>height;
square3=2*PI*radius*radius+2*PI*radius*height; //////////////////基类的成员是radius，没有1，你写成了radius1
cout<<"the cylinder's square is:"<<square3<<endl;
}
virtual void Volume()
{
volume3=PI*radius*radius*height; //////////////////基类的成员是radius，没有1，你写成了radius1
cout<<"the cylinder's volume is:"<<volume3<<endl;
}
private:
double square3,volume3;
int height;
};
int main()
{
//container container1;
int a;
cout<<"Please input a radius=";
cin>>a;
cube cube1(a);
sphere sphere1(a);
cylinder cylinder1(a);
cube1.Volume();
cube1.Square();
sphere1.Volume();
sphere1.Square();
cylinder1.Square();
cylinder1.Volume();
return 0;
}