#include<iostream.h>
class Circle
{public:
Circle(double r){radius=r}
void setradius(double r)
{radius=r;}
double getradius()
{return r;}
double zhouchang()
{
    zhouchang=2*r*3.14;return zhouchang;
}
double mianji()
{
    mianjing=r*r*3.14;return mianji;
}
private:
    double radius;
    double zhouchang;
    double mianji;
};

void main()
{Circle myCircle;
myCircle.setradius(1.1);
cout<<myCircle.zhouchang()<<endl;
cout<<myCircle.mianji()<<endl;
}

double zhouchang()
{
    zhouchang=2*r*3.14;return zhouchang;
}

把r换成radius，下面那个函数也是，还有下次，麻烦贴下结果还有错误