Question

C++编程，求正方形，长方形，三角形，梯形的周长和面积的程序怎么编写。

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Answer 1

#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);

protected:
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 (l)

{

}

double cylinder :: area()
{
return 2 * pi * radius * (radius + length);
}

class sphere : public circle
{
public :
sphere (double r);
virtual double area();
};

sphere :: sphere (double r) : circle(r)
{

}

double sphere :: area()
{

return 4 * pi * radius * radius ;
}

int 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;
}
自己改一下吧，模板都有了，把圆换掉。