poj Pie

http://poj.org/problem?id=3122

 #include<cstdio>
 #include<cstring>
 #include<cmath>
 #define maxn 10010
 #include<algorithm>
 using namespace std;

 const double pi=acos(-1.0);
 const double eps=1e-;
 double r[maxn];
 int n,f;

 int main()
 {
     int t;
     scanf("%d",&t);
     while(t--){
         double max1=;
         scanf("%d%d",&n,&f);
         f++;
         for(int i=; i<n; i++)
         {
             scanf("%lf",&r[i]);
             r[i]*=r[i];
             if(max1<r[i])
             max1=r[i];
         }
         double low=,high=max1,mid;
         while(high-low>eps)
         {
             mid=(high+low)/;
             int ans=;
             for(int i=; i<n; i++)
                 ans+=(int)(r[i]/mid);
             if(ans<f)
                 high=mid;
             else
                 low=mid;
         }
         printf("%.4lf\n",pi*mid);
     }
     return ;
 }