LA 3635 Pie

 1 #include<iostream>  
 2 #include<cstdio>  
 3 #include<cstring> 
 4 #include <cmath> 
 5 #include<stack>
 6 #include<vector>
 7 #include<map> 
 8 #include<set>
 9 #include<queue> 
10 #include<algorithm>  
11 using namespace std;
12 
13 typedef long long LL;
14 const int INF = (1<<30)-1;
15 const int mod=1000000007;
16 const int maxn=1000005;
17 const double pi = 3.14159265359;
18 
19 double a[maxn];
20 int n,f;
21 
22 int ok(double x){
23     int ans = 0;
24     for(int i = 1;i <= n;i++){
25         ans += (int) (a[i] / x);
26     }
27     return ans >= f+1;
28 }
29 
30 int main(){
31     int T;
32     scanf("%d",&T);
33     while(T--){
34         scanf("%d %d",&n,&f);
35         double lb,ub,mid;
36         ub = -1;
37         for(int i =1;i <= n;i++){
38             scanf("%lf",&a[i]);
39             a[i] = a[i] * a[i];
40             ub = max(ub,a[i]);
41         }
42          
43          lb = 0.000;
44         for(int i = 0;i<=100;i++){
45             mid = (lb + ub) / 2;
46             if(ok(mid)) lb = mid;
47             else ub = mid;
48         //    printf("lb = %lf  ub = %lf  mid = %lf\n",lb,ub,mid);
49         }
50         printf("%.4lf\n",lb * pi);
51     }
52     return 0;
53 }