C++ 面向对象程序设计：圆类实现与文件读写

#include #include using namespace std; //点类Point class Point { private: double x; double y; public: Point(double xv=0,double yv=0);/构造函数/ void setX(double xv); /设置X坐标/ void setY(double yv); /设置Y坐标/ double getX() const; /获取X坐标/ double getY() const; /获取Y坐标/ friend ostream & operator << (ostream &out, const Point &p); //运算符<<重载 friend istream & operator >> (istream &in, Point &p); //运算符>>重载 }; class Plane /平面图形基类/ { public: virtual double length()const=0;/周长/ virtual double area()const=0; /面积/ }; //圆类Circle class Circle:public Point,public Plane { private: double radius; protected: static const double PI; public: Circle(double xv=0,double yv=0,double r=0);/构造函数/ void setR(double r); /设置半径/ double getR() const; /获取半径/ double area()const; /面积/ double length()const; /周长/ friend ostream & operator << (ostream &out, const Circle &c); //运算符<<重载 friend istream & operator >> (istream &in, Circle &c); //运算符>>重载 };

/请在这里填写第一部分答案/

void f(Plane const &p) { cout<<p.area()<<endl; cout<<p.length()<<endl; } //主函数 int main(void) { double d1,d2; cin>>d1>>d2; Point p(d1,d2); Circle c;

/请在这里填写第二部分答案/

f(c);
return 0;

}

###输入样例： 1.0 2.1

###输出样例： 30.1907 19.4779

参考答案：

在Point类中添加运算符<<和>>的重载实现：

ostream & operator << (ostream &out, const Point &p) { out<<'('<<p.x<<','<<p.y<<')'; return out; } istream & operator >> (istream &in, Point &p) { in>>p.x>>p.y; return in; }

在Circle类中添加运算符<<和>>的重载实现：

ostream & operator << (ostream &out, const Circle &c) { out<<'圆心坐标为'<<(const Point &)c<<' 半径为'<<c.radius<<endl; return out; } istream & operator >> (istream &in, Circle &c) { in>>(Point &)c>>c.radius; return in; }

在main函数中实现文件读写操作：

double d1,d2; cin>>d1>>d2; Point p(d1,d2); Circle c; cin>>c; ofstream out('Circle.txt'); out<<p<<endl; out<<c<<endl; out.close(); ifstream in('Circle.txt'); in>>p>>c; in.close(); cout<<p<<endl; cout<<c<<endl;

完整代码如下：