求大神，这个怎么改啊，不会了。。。。。
#include <iostream>#include <cstring>
using namespace std
const double pi = 3.14
class circle
{
public:
circle (double r);
double virtual area();
void area_message(string message);
private:
double radius;
};
circle :: circle(double r) : radius(r)
{
}
double circle :: area()
{
return pi * radius * radius;
}
void circle :: area_message (string message)
{
cout << message << area() << endl;
}
class cylinder : public circle
{
public:
cylinder(double r, double l);
virtual double area();
private:
double length;
}
cylinder :: cylinder (double r, double l) : circle(r) : length (1)
{
}
double cylinder :: area()
{
return 2 * pi * radius * (radius + length);
}
class sphere : circle
{
public :
sphere (double r);
double virtual area();
private:
}
sphere :: sphere (double r) : circle(r)
{
}
virtual double sphere :: area()
{
return 4 * pi * radius * radius ;
}
main()
{
char shape;
double radius, height;
circle * ptr;
cout << "Enter a shape (1 = circle, 2 = cylinder, 3 = sphere): "<< endl;
cin >> shape;
if(shape > '0' & shape < '4')
{
cout << "Enter radius" << endl;
cin >> radius;
if(shape = 1 )
{
ptr= new circle(radius);
}
else if(shape = 2)
{
cout << "Enter height" << endl;
cin >> height;
ptr = new cylinder(radius, height);
}
else if (shape = 3)
{
ptr = new sphere (radius);
}
ptr.area_message("The area is : ");
}
else
cout << "Invalid input" << endl;
}
