5_16.cpp

10个比较经典的C++程序。初学者就先多学习学习别人吧。

#include<iostream>
#include<iomanip>
using namespace std;
class Line
{	double x1,x2,y1, y2;
  public:
    Line(){};
    Line(double a,double b,double c,double d)
    {  x1=a;y1=b; x2=c; y2=d;
		   cout<<"线段端点：("<<x1<<","<<y1<<")-("<<x2<<","<<y2<<")"<<endl;
    };
    friend twoline(Line l1,Line l2)		//声明友元函数
    {  double r1=l2.y1*(l2.x2-l1.x1)-l1.y1*(l2.x2-l2.x1)+(l1.x1-l2.x1)*(l2.y2-l2.y1);
       double r2=(l1.y2-l1.y1)*(l2.x2-l2.x1)-(l1.x2-l1.x1)*(l2.y2-l2.y1);
       double r=r1/r2;    double t=((l1.x1-l2.x1)+r*(l1.x2-l1.x1))/(l2.x2-l2.x1);
       if(r>0&&r<1&&t>0&&t<1)		cout<<"两线段相交"<<endl;
       else if  (r>0&&r<1&&t>=1)		cout<<"两线段不相交，一条在另一条的一侧\n";
       else if((r>=1 ||r<=0)&&t>0&&t<1) cout<<"两线段不相交，一条在另一条的一侧\n";
       else							cout<<"两线段不相交．"<<endl;
    }
};
void main()	{ Line A(2,2,18,18),B(1,12,19,5);  twoline(A,B);}