1857. [SCOI2010]传送带【三分套三分】

 1 #include<iostream>
 2 #include<cstring>
 3 #include<cstdlib>
 4 #include<cstdio>
 5 #include<cmath>
 6 using namespace std;
 7 
 8 int Ax,Ay,Bx,By,Cx,Cy,Dx,Dy,P,Q,R;
 9 double eps=1e-8;
10 
11 double cost(double x,double y,double p,double q,double v)
12 {
13     return sqrt((p-x)*(p-x)+(q-y)*(q-y))/v;
14 }
15 
16 double calc(double x,double y,double p,double q)
17 {
18     return cost(Ax,Ay,x,y,P)+cost(x,y,p,q,R)+cost(p,q,Dx,Dy,Q);
19 }
20 
21 double work2(double x,double y)
22 {
23     double lx=Cx,ly=Cy,rx=Dx,ry=Dy;
24     double lmidx,rmidx,lmidy,rmidy,ans1,ans2;
25     while(fabs(rx-lx)>eps || fabs(ry-ly)>eps)
26     {
27         lmidx=lx+(rx-lx)/3.0;
28         rmidx=lx+((rx-lx)/3.0)*2.0;
29         lmidy=ly+(ry-ly)/3.0;
30         rmidy=ly+((ry-ly)/3.0)*2.0;
31         ans1=calc(x,y,lmidx,lmidy);
32         ans2=calc(x,y,rmidx,rmidy);
33         if(ans1>ans2)lx=lmidx,ly=lmidy;
34         else rx=rmidx,ry=rmidy;
35     }
36     return (max(calc(x,y,lx,ly),calc(x,y,rx,ry)));
37 }
38 
39 double work1()
40 {
41     double lx=Ax,ly=Ay,rx=Bx,ry=By;
42     double lmidx,rmidx,lmidy,rmidy,ans1,ans2;
43     while(fabs(rx-lx)>eps || fabs(ry-ly)>eps)
44     {
45         lmidx=lx+(rx-lx)/3.0;
46         rmidx=lx+((rx-lx)/3.0)*2.0;
47         lmidy=ly+(ry-ly)/3.0;
48         rmidy=ly+((ry-ly)/3.0)*2.0;
49         ans1=work2(lmidx,lmidy);
50         ans2=work2(rmidx,rmidy);
51         if(ans1>ans2)lx=lmidx,ly=lmidy;
52         else rx=rmidx,ry=rmidy;
53     }
54     return (max(work2(lx,ly),work2(rx,ry)));
55 }
56 
57 int main()
58 {
59     scanf("%d%d%d%d",&Ax,&Ay,&Bx,&By);
60     scanf("%d%d%d%d",&Cx,&Cy,&Dx,&Dy);
61     scanf("%d%d%d",&P,&Q,&R);
62     printf("%.2lf\n",work1());
63 }