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:

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#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; }