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; }