HDU-2857-Mirror and Light(计算几何)

#include <stdio.h>

void jd(double a1,double b1,double c1,double a2,double b2,double c2,double &x,double &y)//两直线交点
{
    x=(b2*c1-b1*c2)/(a1*b2-a2*b1);
    y=(a2*c1-a1*c2)/(a2*b1-a1*b2);
}

void line(double x1,double y1,double x2,double y2,double &a,double &b,double &c)//两点确定的直线
{
    a=y1-y2;
    b=x2-x1;
    c=x2*y1-x1*y2;
}

int main()
{
    int T;
    double x1,x2,y1,y2,x0,y0,x3,y3,a1,a2,b1,b2,c1,c2,x,y;

    scanf("%d",&T);

    while(T--)
    {
        scanf("%lf%lf%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x0,&y0,&x3,&y3);

        a1=x1-x2;//过(x0,y0)垂直与镜子的直线
        b1=y1-y2;
        c1=x0*x1-x0*x2+y0*y1-y0*y2;

        line(x1,y1,x2,y2,a2,b2,c2);//镜子所在直线

        jd(a1,b1,c1,a2,b2,c2,x,y);//(x,y)上面两条直线的交点

        x+=x-x0;
        y+=y-y0;

        line(x,y,x3,y3,a1,b1,c1);

        jd(a1,b1,c1,a2,b2,c2,x,y);

        printf("%.3f %.3f\n",x,y);
    }
}