P2571 [SCOI2010]传送带

#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
typedef double db;
inline db _min(const db &a,const db &b) {return a<b ?a:b;}
const db eps=1e-7;
struct node{db x,y;}a,b,c,d; //存坐标
db p,q,r;
inline db dist(node &A,node &B) {return sqrt((A.x-B.x)*(A.x-B.x)+(A.y-B.y)*(A.y-B.y));}
inline db F(node &n,node &m) {return dist(a,n)/p+dist(n,m)/r+dist(m,d)/q;} //总距离计算
inline db sec(node &A){
    node l1=c,r1=d,l2,r2; db ans=1e9;
    do{
        l2.x=(l1.x+r1.x)/2.0,l2.y=(l1.y+r1.y)/2.0;
        r2.x=(l2.x+r1.x)/2.0,r2.y=(l2.y+r1.y)/2.0;
        db q1=F(A,l2),q2=F(A,r2);
        if(q1>q2) l1=l2;
        else r1=r2;
        ans=_min(ans,_min(q1,q2));
    }while(fabs(r1.x-l1.x)>=eps||fabs(r1.y-l1.y)>=eps);
    return ans;
}
int main(){
    scanf("%lf%lf%lf%lf",&a.x,&a.y,&b.x,&b.y);
    scanf("%lf%lf%lf%lf",&c.x,&c.y,&d.x,&d.y);
    scanf("%lf%lf%lf",&p,&q,&r);
    node l1=a,r1=b,l2,r2; db ans=1e9;
    do{
        l2.x=(l1.x+r1.x)/2.0,l2.y=(l1.y+r1.y)/2.0; //取中点
        r2.x=(l2.x+r1.x)/2.0,r2.y=(l2.y+r1.y)/2.0; //取四等分点
        db q1=sec(l2),q2=sec(r2); //在cd上三分
        if(q1>q2) l1=l2;
        else r1=r2;
        ans=_min(ans,_min(q1,q2));
    }while(fabs(r1.x-l1.x)>=eps||fabs(r1.y-l1.y)>=eps); //使用do-while循环是防止线段退化成一个点的情况时直接跳出（如a,b重合）
    printf("%.2lf",ans);
    return 0;
}