（补）第十二周实验报告（4）

/* (程序头部注释开始)

* 程序的版权和版本声明部分

* Copyright (c) 2011, 烟台大学计算机学院学生 

* All rights reserved.

* 文件名称：                              

* 作    者：     王      琦                                

* 完成日期：   2012      年   5    月   12   日

* 版 本 号：          

 

* 对任务及求解方法的描述部分 ： 

* 输入描述：类的组合与继承

（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、析构函数及必要的输入输出函数

（4）定义友元函数int locate，判断点p在圆c上、圆c内或圆c外，返回值<0圆内，==0圆上，>0 圆外；

（5）重载关系运算符（6种）运算符，使之能够按圆的面积比较两个圆的大小；

（6）给定一点p，求出该点与圆心相连成的直线与圆的两个交点并输出*/ 

 

* 问题描述：

* 程序输出： 

* 程序头部的注释结束

程序代码：

#include <iostream>
#include <cmath>
using namespace std;
class Point
{
public:
Point(){x=0;y=0;}
Point(double x0,double y0) {x=x0;y=y0;}
~Point(){};
double getX(){return x;}//公共接口
double getY(){return y;}
void setx(double x1){x = x1;}
void sety(double y1){y = y1;}
friend ostream &operator<<(ostream& output,Point &c);
protected:
double x;
double y;
};
ostream &operator<<(ostream& output,Point &c)
{
output<<"Point:("<<c.x <<","<<c.y<<")";
return output;
}

class Cricle:public Point
{
public:
Cricle(){r=0;}
Cricle(double x0,double y0,double r0):Point(x0,y0){r=r0;}
~Cricle(){};
double getR(){return r;}
friend ostream &operator<<(ostream& output,Cricle &c);
friend double locate();
double area();
bool operator>(Cricle &c);
bool operator>=(Cricle &c);
bool operator<(Cricle &c);
bool operator<=(Cricle &c);
bool operator==(Cricle &c);
bool operator!=(Cricle &c);
friend void crossover_point1(Point &p1,Cricle &c1,Point &p4,Point &p5);
protected:
double r;
};
ostream &operator<<(ostream& output,Cricle  &c)
{
output<<"圆心为："<<"("<<c.getX()<<","<<c.getY()<<"),"<<"半径为："<<c.r<<endl;
return output;
}
double locate(Point p,Cricle c)
{
double d;
d=(c.getX()-p.getX())*(c.getX()-p.getX())+(c.getY()-p.getY())*(c.getY()-p.getY());
return (c.getR()*c.getR()-d);
}
double Cricle::area()
{
return r*r*3.1415926;
}

bool Cricle::operator>(Cricle &c)
{
if(area()>c.area())
return true;
return false;
}
bool Cricle::operator>=(Cricle &c)
{
if(area()<c.area())
return false;
return true;
}
bool Cricle::operator<(Cricle &c)
{
if(area()<c.area())
return true;
return false;
}
bool Cricle::operator<=(Cricle &c)
{
if(area()>c.area())
return false;
return true;
}
bool Cricle::operator==(Cricle &c)
{
if(area()==c.area())
return true;
return false;
}
bool Cricle::operator!=(Cricle &c)
{
if(area()==c.area())
return false;
return true;
}
void crossover_point1(Point &p1,Cricle &c1,Point &p4,Point &p5)
{
double d;
d = c1.getX() + (p1.getX() - c1.getX()) * c1.getR() / sqrt((p1.getX() - c1.getX()) * (p1.getX() - c1.getX()) + (p1.getY() - c1.getY()) * (p1.getY() - c1.getY()));
p4.setx(d);

d = c1.getX() - (p1.getX() - c1.getX()) * c1.getR() / sqrt((p1.getX() - c1.getX()) * (p1.getX() - c1.getX()) + (p1.getY() - c1.getY()) * (p1.getY() - c1.getY()));
p5.setx(d);

d = c1.getY() + (p1.getY() - c1.getY()) * c1.getR() / sqrt((p1.getX() - c1.getX()) * (p1.getX() - c1.getX()) + (p1.getY() - c1.getY()) * (p1.getY() - c1.getY()));
p4.sety(d);

d = c1.getY() - (p1.getY() - c1.getY()) * c1.getR() / sqrt((p1.getX() - c1.getX()) * (p1.getX() - c1.getX()) + (p1.getY() - c1.getY()) * (p1.getY() - c1.getY()));
p5.sety(d);
}
int main( )
{
Cricle 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;
cout<<endl;

cout<<"圆c1: "<<c1;
if(c1>c2) cout<<"大于"<<endl;
if(c1<c2) cout<<"小于"<<endl;
if(c1>=c2) cout<<"大于等于"<<endl;
if(c1<=c2) cout<<"小于等于"<<endl;
if(c1==c2) cout<<"等于"<<endl;
if(c1!=c2) cout<<"不等于"<<endl;
cout<<"圆c2: "<<c1;
cout<<endl;

Point p4,p5;
crossover_point1(p1,c1, p4, p5);

cout<<"点p1: "<<p1;
cout<<"与圆c1: "<<c1;
cout<<"的圆心相连，与圆交于两点，分别是："<<endl;
cout<<"交点: "<<p4<<endl;
cout<<"交点: "<<p5;
cout<<endl;

system("pause");
return 0;
}

运行显示：

圆c1: 圆心为：(3,2),半径为：4

点p1: Point:(1,1)点p1在圆c1之外

点p2: Point:(3,-2)点p2在圆c1之上

点p3: Point:(7,3)点p3在圆c1之内

圆c1: 圆心为：(3,2),半径为：4

小于

小于等于

不等于

圆c2: 圆心为：(3,2),半径为：4

点p1: Point:(1,1)与圆c1: 圆心为：(3,2),半径为：4

的圆心相连，与圆交于两点，分别是：

交点: Point:(-0.577709,0.211146)

交点: Point:(6.57771,3.78885)

请按任意键继续. . .

上机感想：

我认为难点还是在定义成员函数时的那些算法，不去看的话，自己很难想的出来。或许自己不大擅长计算。