题目: 

#include 
     
      #include 
      
       using namespace std;const double PI = acos(-1);double v[10005];int N, F;bool test(double x){    int tot = 0;    for(int i=0; i
       
        = F;}int main (){    int T, r;    scanf("%d", &T);    while(T--) {        scanf("%d%d", &N, &F);        ++F;        double lb = 0, ub = -1;         for(int i=0; i
        
          ub)    ub = v[i];        }                ub += 1;        while(lb + 1e-5< ub) { // [, )            double mid = (lb + ub) / 2;            if(test(mid))    lb = mid;            else ub = mid;        }        printf("%.4lf\n", lb);    }    return 0;}