TZOJ3133: 求对称点

#include<stdio.h>
int main()
{
    double a,b,c,d,e,f,g,h,i;
    while(~scanf("%lf %lf %lf %lf %lf %lf",&a,&b,&c,&d,&e,&f))
    {
        double x,y,x1,y1,k1,k2,b1,x2,y2,x3,y3;
        x=a;
        y=b;
        x1=a+c;
        y1=b+d;
        if(x1==x)
        {
            if(e>x)x2=x-(e-x);
            else x2=x+(x-e);
            y2=f;
        }
        else 
        {
            k1=(y1-y)*1.0/(x1-x);
              b1=y-k1*x*1.0;
              g=k1;
              h=-1;
              i=b1;
            x2=(h*h*e-g*g*e-2*g*h*f-2*g*i)*1.0/(g*g+h*h);
            y2=(g*g*f-h*h*f-2*g*h*e-2*h*i)*1.0/(g*g+h*h);
        }
        if(x2>0)x3=(int)(x2*100.0+0.5);
        else x3=(int)(x2*100.0-0.5);
        if(y2>0)y3=(int)(y2*100.0+0.5);
        else y3=(int)(y2*100.0-0.5);
        printf("%.2f %.2f\n",x3/100.0,y3/100.0);
    }
    return 0;
}