第十二周 项目4-点，圆的关系

 /* *Copyright (c) 2015,烟台大学计算机学院 *All rights reserved. *文件名称:time.cpp *作者:刘天恩 *完成时间:2015年5月25号 *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:无 *程序输出:输出圆的基本信息 */#include <iostream>#include<cmath>using namespace std;class Point{public:    Point():x(0),y(0){}    Point(int x0,int y0):x(x0),y(y0){}    ~Point(){}    double distance(Point P);    friend ostream&operator<<(ostream&,Point&);protected:    int x,y;};double Point::distance(Point P){    double dx=x-P.x;    double dy=y-P.y;    return sqrt(dx*dx+dy*dy);}ostream&operator<<(ostream&output,Point&P){    output<<"["<<P.x<<","<<P.y<<"]"<<endl;    return output;}class Circle:public Point{public:    Circle(int x0,int y0,int r0):        Point(x0,y0),r(r0){}    ~Circle(){}    friend int locate(Point &,Circle &);    friend ostream&operator<<(ostream&,Circle&);protected:    int r;};int locate(Point &P,Circle &C){    Point p(C.x,C.y);  //圆心    double d=p.distance(P);  //点到圆心的距离    if(abs(d-C.r)<1e-7)        return 0;   //点在圆上    else if(abs(d<C.r))        return -1;   //点在圆内    else        return 1;   //点在圆外}ostream&operator<<(ostream&output,Circle&C){    output<<"圆心：["<<C.x<<","<<C.y<<"]"<<"   半径："<<C.r<<endl;    return output;}int main( ){Circle c1(3,2,4),c2(4,5,5);      //c2应该大于c1Point 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;}

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