poj1269---直线位置关系

题目大意：给你8个点，也就是两条直线，让你判断他们的位置关系

 

代码如下:

#include <iostream>
#include<cstdio>
#include<cmath>
using namespace std;
#define EPS 1e-8
struct Point
{
    double x,y;
}a,b,c,d;
double xmult(Point p1,Point p2,Point p0)
{
    return (p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y);
}

Point intersection(Point A, Point B, Point C, Point D)
{
    //a1*x+b1*y=c1;a2*x+b2*y=c2;
    Point ans;
    double a1 = A.y-B.y;
    double b1 = B.x-A.x;
    double c1 = A.x*B.y-B.x*A.y;
    double a2 = C.y-D.y;
    double b2 = D.x-C.x;
    double c2 = C.x*D.y-D.x*C.y;
    double x = (b1*c2-b2*c1)/(a1*b2-a2*b1);
    double y = (a2*c1-a1*c2)/(a1*b2-a2*b1);
    ans.x=x,ans.y=y;
    return ans;
}
int main()
{
    //freopen("in.txt","r",stdin);
    int T;
    cin>>T;
    printf("INTERSECTING LINES OUTPUT\n");
    while(T--)
    {
        scanf("%lf%lf%lf%lf%lf%lf%lf%lf",&a.x,&a.y,&b.x,&b.y,&c.x,&c.y,&d.x,&d.y);
        if(fabs(xmult(a,b,c))<=EPS&&fabs(xmult(a,b,d)<=EPS))
            printf("LINE\n");//直线重合
        else if((a.y-b.y)*(d.x-c.x)==(b.x-a.x)*(c.y-d.y))
            printf("NONE\n");//直线平行
        else
        {
            Point ans = intersection(a,b,c,d);
            printf("POINT %.2f %.2f\n",ans.x,ans.y);
        }
    }
    printf("END OF OUTPUT\n");
    return 0;
}