13周 工程1 点，全面关系

#include <iostream>
#include <cmath>
using namespace std;
class Point
{

public:
Point(double a,double b):x(a),y(b) {}
double getx()
{
return x;
}
double gety()
{
return y;
}
friend ostream&operator << (ostream&,Point&);
protected:
double x,y;
};
ostream&operator << (ostream &output,Point &p)
{
output<<"("<<p.getx()<<","<<p.gety()<<")"<<endl;
return output;
}
class Circle:public Point
{

public:
Circle(double a,double b,double c):Point(a,b),r(c) {}
double getr()
{
return r;
}
friend ostream&operator << (ostream&,Circle&);
friend double locate(Circle&,Point&);
protected:
double r;
};
ostream&operator << (ostream &output,Circle &c)
{
output<<"("<<c.getx()<<","<<c.gety()<<")"<<" ";
output<<"r="<<c.getr()<<endl;
return output;
}
double locate(Point &po,Circle &ci)
{
double d,num;
d=sqrt(pow((ci.getx()-po.getx()),2)+pow((ci.gety()-po.gety()),2));
if(d>ci.getr())
num=1;
else if(d==ci.getr())
num=0;
else
num=-1;
return num;
}
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;
}