CodeForces 590B Chip 'n Dale Rescue Rangers

这题可以o(1)推出公式，也可以二分答案+验证。

#include<iostream>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<cstdio>
using namespace std;

double X1,X2,Y1,Y2;
double v,t;
double vx,vy,wx,wy;

bool check(double mid)
{
    double tmpx,tmpy;
    if(mid<=t)
    {
        tmpx=X1+mid*vx;
        tmpy=Y1+mid*vy;
        double dis=sqrt((X2-tmpx)*(X2-tmpx)+(Y2-tmpy)*(Y2-tmpy));
        if(dis/v>mid) return 0;
        return 1;
    }
    else
    {
        tmpx=X1+t*vx;
        tmpy=Y1+t*vy;

        tmpx=tmpx+(mid-t)*wx;
        tmpy=tmpy+(mid-t)*wy;

        double dis=sqrt((X2-tmpx)*(X2-tmpx)+(Y2-tmpy)*(Y2-tmpy));
        if(dis/v>mid) return 0;
        return 1;
    }
}

int main()
{
    scanf("%lf%lf%lf%lf",&X1,&Y1,&X2,&Y2);
    scanf("%lf%lf",&v,&t);
    scanf("%lf%lf%lf%lf",&vx,&vy,&wx,&wy);

    double l=0,r=9999999999;
    double ans;
    int t=200;

    while(t--)
    {
        double mid=(l+r)/2.0;

        if(check(mid))
        {
            ans=mid;
            r=mid;
        }
        else l=mid;
    }
    printf("%.18lf
",ans);
    return 0;
}