C++(一) --圆的面积

//求圆的面积

#include <iostream>

#define pi 3.1415926

using namespace std;

class Circle

{

    double r;

    double s;

public:

    Circle(double rr){r=rr;}

    Circle();

    ~Circle(){}

    double area(){s=pi*r*r;return s;}

};

int main()

{

    double r1;

    cout << "输入圆的半径：";

    cin>>r1;

    Circle c(r1);

    cout<<"求得圆的面积为："<<c.area()<<endl;

    return 0;

}

//求圆的面积

#include <iostream>

#define pi 3.1415926

using namespace std;

class Circle

{

    double r;

    double s;

public:

    Circle(double rr){r=rr;}

    Circle();

    ~Circle(){}

    double area(){s=pi*r*r;return s;}

};

int main()

{

    double r1;

    cout << "输入圆的半径：";

    cin>>r1;

    Circle c(r1);

    cout<<"求得圆的面积为："<<c.area()<<endl;

    return 0;

}