使用面向对象思想
#include <iostream>
#include <iomanip>
#define PI 3.14159
using namespace std;
class Circle {
public:
Circle(double radius): _radius(radius){}
// 计算周长
double girth() {
return _radius * 2 * PI;
}
// 计算面积
double area() {
return _radius * _radius * PI;
}
private:
double _radius;
};
int main() {
double radius;
cin >> radius;
Circle circle(radius);
cout << fixed << setprecision(6) << circle.girth() << endl;
cout << fixed << setprecision(6) << circle.area() << endl;
return 0;
}