第十二周（点圆类）

/*
*copyright(c) 2015,烟台大学计算机学院
*All rights reserved。
*文件名称：第十二周（点圆类）

*作者：王忠
*完成日期：2015.5.27

*版本号：v1.0
*
*问题描述：（1）先建立一个Point(点)类，包含数据成员x,y(坐标点)；
（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）；

*输入描述：

*程序输出：

#include<iostream>#include<Cmath>using namespace std;class Point //定义坐标点类{public:    Point():x(0),y(0) {};    Point(double x0, double y0):x(x0), y(y0) {};    friend ostream& operator <<(ostream &output,Point &p);    double distance(Point &p);protected:    double x,y;   //点的横坐标和纵坐标};class Circle:public Point{public:    Circle(double x,double y,double z):Point(x,y),r(z) {}    friend istream& operator >>(istream &input,Circle &c);    friend ostream& operator <<(ostream &output,Circle &c);    friend int locate(Point &p, Circle &c);protected:    double r;};ostream& operator <<(ostream &output,Point &p){    output<<"Point: ("<<p.x<<","<<p.y<<")"<<endl;    return output;}double Point::distance(Point &p){    double dx = x-p.x;    double dy = y-p.y;    return sqrt(dx*dx+dy*dy);}istream& operator >>(istream &input,Circle &c){    double a,b,d;    cout<<"输入半径，圆心坐标：";    input>>a>>b>>d;    Circle(a,b,d);    return input;}ostream& operator <<(ostream &output,Circle &c){    output<<"Circle: ("<<c.r<<","<<c.x<<","<<c.y<<")"<<endl;    return output;}int locate(Point &p,Circle &c){    Point cp(c.x,c.y);    double d = cp.distance(p);    if (d==c.r)        return 0;    else if (d < c.r)        return -1;    else        return 1;}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;}