1 #include 
      
        2 #include
       
         3 #include
        
          4 #include
         
           5 #include
          
            6 #define eps 1e-8 7 #define pi 3.14159265359//精度高一点 6位错了一次 8 using namespace std; 9 int main()10 {11     int i,j,n,f,t;12     double r[10005];13     cin>>t;14     while(t--)15     {16         cin>>n>>f;17         double low=0.0,high = 0.0;18         for(i = 1; i <= n ; i++)19         {20             cin>>r[i];21             if((r[i]*r[i])>high)22                 high = r[i]*r[i];23         }24         double mid = (low+high)/2;25         while(low+eps
           
            =(f+1))33 low = mid ;34 else35 high = mid;36 mid = (low+high)/2;37 }38 printf("%.4lf\n",pi*mid+eps);39 }40 return 0;41 }