编写一个圆类Circle,其中包含1个数据成员表示半径，3个成员函数分别实现半径的输入、面积的计算、半径和面

Question

(接上）积的输出，并编写相应的main()函数测试该类。

Answer 1

#include<iostream.h>

class circle
{
private:
int r;
public:
void input()
{
cout<<"输入半径"<<endl;
cin>>r;
}

double S()
{
return 3.14*r*r;
}

void output()
{
cout<<"半径: "<<r<<","<<"面积: "<<S();
}
};

void main()
{
circle circle11;
double r,R;
circle11.input();
circle11.S();
circle11.output();
}

Answer 2

const double PI = 3.14;

class Circle
{
private:
double radius;
public:
Circle(int r):radius(r){}
void SetRadiusValue(int x){radius = x;}
double ComputeArea(){return PI*radius*radius;}
void Print(){cout << "Radius = " << radius << ", Area = " << ComputeArea() << endl;}
};

int main()
{
Circle circle(1);
circle.Print();

circle.SetRadiusValue(2);
circle.Print();

return 0;
}

Answer 3

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