HDU4024 Dwarven Sniper’s hunting [二分]

　　简单二分，最大射击距离是必然能达到的，只要在能到达最大距离的瞬间就立刻射击可以保证时间最短。

　　

#include <string.h>
#include <stdio.h>
#include <math.h>
double xx1,yy1,xx2,yy2,lx,ly,vd,vb,l;
double sqr(double x){return x*x;}
double getdis(double xx1,double yy1,double xx2,double yy2){
    return sqrt(sqr(xx1-xx2)+sqr(yy1-yy2));
}
int canreach(double t){
    double dis=getdis(xx2,yy2,xx1+t*lx,yy1+t*ly);
    return vd*(t-l/vb)>=fabs(dis-l);
}
int main(){
    freopen("test.in","r",stdin);
    while(scanf("%lf%lf%lf%lf%lf%lf%lf%lf%lf",&xx1,&yy1,&xx2,&yy2,&lx,&ly,&vd,&vb,&l)){
        if(xx1+yy1+xx2+yy2+lx+ly+vd+vb+l==0)break;
        double low=l/vb,high=1e9,mid;
        while(high-low>1e-7){
            mid=(low+high)/2;
            if(canreach(mid))high=mid;
            else low=mid;
        }
        printf("%.3f %.3f\n",l,mid);
    }
    return 0;
}