第12周 【项目4 - 点、圆的关系】（2）

问题描述：

【项目4 - 点、圆的关系】

<strong><span style="font-family:KaiTi_GB2312;font-size:18px;color:#ff6666;">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;
}</span></strong>

（5）在圆类上重载关系运算符（6种），使之能够按圆的面积比较两个圆的大小。自编main函数完成测试。

代码：

#include <iostream>
#include <cmath>
using namespace std;
class Point{
protected:
    double x,y;
public:
    Point(){x=0,y=0;}
    Point(double a,double b):x(a),y(b){}
    double getx(){return x;}
    double gety(){return y;}
    double distance(const Point& c){
        double dx = x-c.x;
        double dy = y-c.y;
        return sqrt(dx*dx+dy*dy);
    }
    friend istream&operator>>(istream& in,Point & c);
    friend ostream&operator<<(ostream& out,const Point& c);
};
istream& operator>>(istream& in,Point & c){
    cout<<"请输入点坐标（x，y）格式\n";
    char a,b,e;
    do{
        cin>>a>>c.x>>b>>c.y>>e;
        if(a=='('&&b==','&&e==')')
            break;
        cout<<"格式错误请重新输入！\n";
    } while(1);
    return in;
}
ostream& operator<<(ostream& out,const Point & c){
    cout<<"("<<c.x<<","<<c.y<<")\n";
    return out;
}
class Circle:public Point{
private:
    double r;
public:
    Circle():r(0){Point();}
    Circle(double a,double b,double c):Point(a,b),r(c){}
    friend istream&operator>>(istream& in,Circle & c);
    friend ostream&operator<<(ostream& out,const Circle& c);
    friend int locate(Point&,Circle&  );
    bool operator>(const Circle&);
    bool operator<(const Circle&);
    bool operator>=(const Circle&);
    bool operator<=(const Circle&);
    bool operator==(const Circle&);
    bool operator!=(const Circle&);
    double area(){
        return 3.14159*r*r;
    }
};
bool Circle::operator>(const Circle& c){
    if(r>c.r)
        return true;
    return false;
}
bool Circle::operator<(const Circle& c){
    if(r<c.r)
        return true;
    return false;
}
bool Circle::operator>=(const Circle& c){
    if(r<c.r)
        return false;
    return true;
}
bool Circle::operator<=(const Circle& c){
    if(r>c.r)
        return false;
    return true;
}
bool Circle::operator==(const Circle& c){
    if(r==c.r)
        return true;
    return false;
}
bool Circle::operator!=(const Circle& c){
    if(r==c.r)
        return false;
    return true;
}
istream&operator>>(istream& in,Circle& c){
    Point d;
    cin>>d;
    c.x=d.getx();
    c.y=d.gety();
    cout<<"请输入半径：";
    cin>>c.r;
    return in;
}
ostream&operator<<(ostream& out,const Circle& c){
    cout<<"("<<c.x<<","<<c.y<<") 半径="<<c.r<<'\12';
    return out;
}
int locate(Point&t2,Circle&t1){
    Point t=t1;
    double x=t1.distance(t2);
    if (abs(x-t1.r)<1e-7)
        return 0;
    else if (x<t1.r)
        return -1;
    else
        return 1;
}
int main( ){
	Circle c1(3,2,4),c2(4,5,5);      //c2应该大于c1
    cout<<"圆c1( "<<c1<<" )的面积是 "<<c1.area()<<endl;
    cout<<"圆c2( "<<c2<<" )的面积是 "<<c2.area()<<endl;
    cout<<"圆c1 ";
    if(c1>c2) cout<<"大于, ";
    if(c1<c2) cout<<"小于, ";
    if(c1>=c2) cout<<"大于等于, ";
    if(c1<=c2) cout<<"小于等于, ";
    if(c1==c2) cout<<"等于, ";
    if(c1!=c2) cout<<"不等于, ";
    cout<<"圆c2"<<endl;

    return 0;
	return 0;
}

运行结果：