BZOJ 1857 传送带

Posted 2020-08-31 ziliuziliu

三分套三分。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#define eps 1e-4
using namespace std;
double x,y,v1,v2,v0;
struct point
{
    double x,y;
    point (double x,double y):x(x),y(y) {}
    point () {}
}a,b,c,d;
double dis(point x,point y)
{
    return sqrt((x.x-y.x)*(x.x-y.x)+(x.y-y.y)*(x.y-y.y));
}
double calc(point x)
{
    point l=c,r=d,k1,k2;
    while (fabs(r.x-l.x)>eps || fabs(r.y-l.y)>eps)
    {
        k1=point(l.x+(r.x-l.x)/3,l.y+(r.y-l.y)/3);
        k2=point(l.x+(r.x-l.x)/3*2,l.y+(r.y-l.y)/3*2);
        if (dis(x,k1)/v0+dis(k1,d)/v2>dis(x,k2)/v0+dis(k2,d)/v2) l=k1;else r=k2;
    }
    return dis(x,l)/v0+dis(l,d)/v2;
}
int main()
{
    scanf("%lf%lf",&x,&y);a=point(x,y);
    scanf("%lf%lf",&x,&y);b=point(x,y);
    scanf("%lf%lf",&x,&y);c=point(x,y);
    scanf("%lf%lf",&x,&y);d=point(x,y);    
    scanf("%lf%lf%lf",&v1,&v2,&v0);
    point l=a,r=b,k1,k2;
    while (fabs(r.x-l.x)>eps || fabs(r.y-l.y)>eps)
    {
        k1=point(l.x+(r.x-l.x)/3,l.y+(r.y-l.y)/3);
        k2=point(l.x+(r.x-l.x)/3*2,l.y+(r.y-l.y)/3*2);
        if (calc(k1)+dis(a,k1)/v1>calc(k2)+dis(a,k2)/v1) l=k1;else r=k2;
    }
    printf("%.2lf\n",calc(l)+dis(a,l)/v1);
    return 0;
}