LA 3635 派

 1 #include <bits/stdc++.h>
 2 
 3 using namespace std;
 4 
 5 const int maxn = 10000 + 5;
 6 const double PI = acos(-1.0);
 7 
 8 int n,f;
 9 double A[maxn];
10 
11 bool ok(double x) {
12     int sum = 0;
13     for(int i=0;i<n;i++) {
14         sum +=(A[i]/x);
15     }
16     if(sum>=f+1)
17         return true;
18     return false;
19 }
20 
21 int main()
22 {
23     int t;
24     scanf("%d",&t);
25     while(t--) {
26         scanf("%d%d",&n,&f);
27         double l=0;
28         double r=-1;
29         for(int i=0;i<n;i++) {
30             int x;
31             scanf("%d",&x);
32             A[i] = PI*x*x;
33             r=max(r,A[i]);
34         }
35 
36         while(r-l>1e-5) {
37             double M = (l+r)/2;
38             if(ok(M)) l = M;
39             else r = M;
40         }
41         printf("%.4lf\n",l);
42     }
43     return 0;
44 }