第12周上机实践项目4——点、园的关系（1）

（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）；

代码

#include <iostream>
#include <cmath>
using namespace std;
class Point
{
protected:
    double x,y;
public:
    Point(double xx,double yy):x(xx),y(yy) {}
    double getx(){return x;}
    double gety(){return y;}
    friend ostream & operator<<(ostream &,const Point &);
};
ostream & operator<<(ostream &output,const Point &p)
{
    output<<"["<<p.x<<","<<p.y<<"]"<<endl;
    return output;
}
class Circle:public Point
{
protected:
    double r;
public:
    Circle(double xx,double yy,double rr):Point(xx,yy),r(rr) {}
    friend ostream &operator<<(ostream &out,Circle &c);
    friend int locate(Point &p,Circle &c);
};
ostream &operator<<(ostream &out,Circle &c)
{
    out<<"圆心=("<<c.getx()<<","<<c.gety()<<") 半径="<<c.r<<endl;
    return out;
}
int locate(Point &p,Circle &c)
{
    double x=p.getx()-c.getx(),y=p.gety()-c.gety(),s;
    s=sqrt(x*x+y*y);
    if(abs(s-c.r)<=0.00001)
        return 0;
    else if(s>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;
}

第12周上机实践项目4——点、园的关系（1）

原文：http://blog.csdn.net/blue_skyrim/article/details/46238921