Cylinder

http://acm.sdut.edu.cn/sdutoj/problem.php?action=showproblem&problemid=2374

思路：三分枚举。

 #include <cstdio>
 #include <cmath>
 #include <cstring>
 #include <algorithm>
 #define maxn 1000100
 using namespace std;
 const double eps=1e-;
 const double pi=acos(-1.0);

 double w,h;

 double ok(double x,int flag)
 {
     double max1=;
     double k=h;
     double s=w;
     double r=(x>s)?s:x;
     double ss=pi*(r/)*(r/);
     double ll=pi*r;
     double c=k-x;
     double r1=(k-x)>s?s:(k-x);
     if(s>=ll&&flag==)
     {
         double v1=ss*c;
         max1=max(max1,v1);
     }
     if(c>=ll&&flag==)
     {
         double v2=ss*s;
         max1=max(max1,v2);
     }
     double s1=pi*(r1/)*(r1/);
     double l1=pi*r1;
     if(s>=l1&&flag==)
     {
         double v3=s1*x;
         max1=max(v3,max1);
     }
     if(x>=l1&&flag==)
     {
         double v4=s1*s;
         max1=max(max1,v4);
     }
     return max1;
 }

 int main()
 {
     while(scanf("%lf%lf",&w,&h)!=EOF)
     {
         if(w==&&h==) break;
         double l=,r=h;
         double ans=,ans1=;
         while(r-l>eps)
         {
             double mid1=(r+l)/;
             double mid2=(l+mid1)/;
             if(ok(mid1,)>=ok(mid2,))
             {
                 ans=mid1;
                 l=mid2;
             }
             else
                 r=mid1;
         }
         l=,r=w;
         while(r-l>eps)
         {
             double mid1=(r+l)/;
             double mid2=(l+mid1)/;
             if(ok(mid1,)>=ok(mid2,))
             {
                 ans1=mid1;
                 l=mid2;
             }
             else
                 r=mid1;
         }
         printf("%.3lf\n",max(ok(ans,),ok(ans1,)));
     }
     return ;
 }