(2)以Point为基类,派生出一个Circle(圆)类,增加数据成员(半径),基类的成员表示圆心;
(3)编写上述两类中的构造、析构函数及必要运算符重载函数(本项目主要是输入输出);
(4)定义友元函数int locate,判断点p与圆的位置关系(返回值<0圆内,==0圆上,>0 圆外);
#include <iostream> #include <cmath> using namespace std; class Point { public: Point():x(0),y(0){} Point(double a,double b):x(a),y(b){} double distance(const Point &p)const; friend ostream & operator<<(ostream &,const Point &); protected: double x; double y; }; double Point::distance(const Point &p) const { double dx = x-p.x; double dy = y-p.y; return sqrt(dx*dx+dy*dy); } ostream & operator<<(ostream &output,const Point &p) { output<<"["<<p.x<<","<<p.y<<"]"<<endl; return output; } class Circle:public Point { public: Circle():Point(),radius(1){}; Circle(double a,double b,double r):Point(a,b),radius(r){} friend ostream &operator<<(ostream &,const Circle &); friend int locate(const Point &p, const Circle &c); //判断点p在圆上、圆内或圆外,返回值:<0圆内,==0圆上,>0 圆外 protected: double radius; }; ostream &operator<<(ostream &output,const Circle &c) { output<<"Center=["<<c.x<<", "<<c.y<<"], r="<<c.radius<<endl; return output; } int locate(const Point &p, const Circle &c) { const Point cp(c.x,c.y); //圆心 double d = cp.distance(p); if (abs(d - c.radius) < 1e-7) return 0; //相等 else if (d < c.radius) return -1; //圆内 else return 1; //圆外 } int main( ) { Circle c1(3,2,4),c2(4,5,5); //c2应该大于c1 Point p1(1,1),p2(3,-2),p3(7,3); //分别位于c1内、上、外 cout<<"圆c1: "<<c1; cout<<"点p1: "<<p1; cout<<"点p1在圆c1之"<<((locate(p1, c1)>0)?"外":((locate(p1, c1)<0)?"内":"上"))<<endl; cout<<"点p2: "<<p2; cout<<"点p2在圆c1之"<<((locate(p2, c1)>0)?"外":((locate(p2, c1)<0)?"内":"上"))<<endl; cout<<"点p3: "<<p3; cout<<"点p3在圆c1之"<<((locate(p3, c1)>0)?"外":((locate(p3, c1)<0)?"内":"上"))<<endl; return 0; }运行结果: