定义一个圆类(Circle),属性为半径(radius)、圆周长和面积,操作为输入半径并计算周长、面积,输出半径、周长

#include
#include
using namespace std;
class Circle{
double r,Area,Circumference;
public:
Circle(double a=0);
Circle(Circle &);

void SetR(double R);
double GetR(){return r;}
double GetAreaCircle(){return Area;}
double GetCircumference(){return Circumference;}
};
Circle::Circle(double a){
r=a;
Area=r*r*3.14159265;
Circumference=2*r*3.14159265;
}
Circle::Circle(Circle & cl){
r=cl.r;
Area=cl.Area;
Circumference=cl.Circumference;
}

void Circle::SetR(double R){
r=R;
Area=r*r*3.14159265;
Circumference=2*r*3.14159265;
}

int main(){
Circle cl1(2),cl2,cl3=cl1;
cout<<"圆半径:"< <<'\t'<<"圆面积:"< cl2.SetR(4);
cout<<"圆半径:"< <<'\t'<<"圆面积:"< return 0;
}

#include
#define PI 3.14159
struct circle
{double radius;
double perimeter;
double area;}circle;
void main()
{scanf("%d\n",&radius);
perimeter=2*PI*radius;
area=PI*radius*radius;
printf("%d\n%d\n",perimeter,area);
}