BZOJ1857: [Scoi2010]传送带

题目：http://www.lydsy.com/JudgeOnline/problem.php?id=1857

三分套三分。

#include<cstring>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstdio>
#include<cmath>
#include<queue>
#define rep(i,l,r) for (int i=l;i<=r;i++)
#define down(i,l,r) for (int i=l;i>=r;i--)
#define clr(x,y) memset(x,y,sizeof(x))
#define maxn 100500
#define eps 1e-3
#define ll long long
using namespace std;
double ax,ay,bx,by,cx,cy,dx,dy,p,q,r;
int read(){
    int x=0,f=1; char ch=getchar();
    while (!isdigit(ch)) {if (ch=='-') f=-1; ch=getchar();}
    while (isdigit(ch)) {x=x*10+ch-'0'; ch=getchar();}
    return x*f;
}
double sqr(double x){
    return x*x;
}
double dis(double x,double y,double xx,double yy){
    return sqrt(sqr(x-xx)+sqr(y-yy));
}
double cal(double x,double y){
    double lx=cx,ly=cy,rx=dx,ry=dy;
    while (fabs(lx-rx)>=eps||fabs(ly-ry)>=eps){
        double mx=(rx-lx)/3,my=(ry-ly)/3;
        double t1=dis(ax,ay,x,y)/p+dis(x,y,lx+mx,ly+my)/r+dis(lx+mx,ly+my,dx,dy)/q;
        double t2=dis(ax,ay,x,y)/p+dis(x,y,lx+mx*2,ly+my*2)/r+dis(lx+mx*2,ly+my*2,dx,dy)/q;
        if (t1<t2) {rx=lx+mx*2,ry=ly+my*2;}
        else {lx=lx+mx; ly=ly+my;}
    }
    return dis(ax,ay,x,y)/p+dis(x,y,lx,ly)/r+dis(lx,ly,dx,dy)/q;
}
int main(){
    scanf("%lf%lf%lf%lf",&ax,&ay,&bx,&by);
    scanf("%lf%lf%lf%lf",&cx,&cy,&dx,&dy);
    scanf("%lf%lf%lf",&p,&q,&r);
    double lx=ax,ly=ay,rx=bx,ry=by;
    while (fabs(lx-rx)>=eps||fabs(ly-ry)>=eps){
        double mx=(rx-lx)/3,my=(ry-ly)/3;
        double t1=cal(lx+mx,ly+my),t2=cal(lx+mx*2,ly+my*2);
        if (t1<t2) {rx=lx+mx*2,ry=ly+my*2;}
        else {lx=lx+mx; ly=ly+my;}
    }
    printf("%.2lf\n",cal(lx,ly));
    return 0;
}