poj 1269 Intersecting Lines (基础数学几何 直线位置)

给你两条直线(前几次wa都理解成线段了)，求 位置状况

1.相离(如果是直线也就是平行）

2.共线

3.相交

 

附上AC代码

#include <stdio.h>
#include <math.h>
struct point{
	double x , y;
};
struct line{
	point l , r;
}t1,t2;
double xmul(point t,point l,point r){
	double x1 , x2 , y1 , y2;
	x1 = l.x - t.x; y1 = l.y - t.y;
	x2 = r.x - t.x; y2 = r.y - t.y;
	return x1 * y2 - x2 * y1;
}
point solve(point u1,point u2,point v1,point v2){
	point ret = u1;
	double t = ((u1.x-v1.x)*(v1.y-v2.y)-(u1.y-v1.y)*(v1.x-v2.x))
					/((u1.x-u2.x)*(v1.y-v2.y)-(u1.y-u2.y)*(v1.x-v2.x));
	ret.x += (u2.x - u1.x) * t;
	ret.y += (u2.y - u1.y) * t;
	return ret;
}
int n;
int main(){
	scanf("%d",&n);
	printf("INTERSECTING LINES OUTPUT\n");
	for(int i = 0 ; i < n ; i++){
		scanf("%lf%lf%lf%lf",&t1.l.x,&t1.l.y,&t1.r.x,&t1.r.y);
		scanf("%lf%lf%lf%lf",&t2.l.x,&t2.l.y,&t2.r.x,&t2.r.y);
		if(xmul(t2.l,t1.l,t1.r)==0&&xmul(t2.r,t1.l,t1.r)==0){
			printf("LINE\n");
		}else if(xmul(t2.l,t1.l,t1.r)==xmul(t2.r,t1.l,t1.r)){
			printf("NONE\n");
		}else{
			point ans = solve(t1.l,t1.r,t2.l,t2.r); 
			printf("POINT %.2lf %.2lf\n",ans.x,ans.y);
		}	
	}
	printf("END OF OUTPUT\n");
	return 0;
}