【HDOJ】1969 Pie

二分。

 #include <stdio.h>
 #include <math.h>

 const double eps = 1e-;
 double areas[];

 int main() {
     int case_n, n, f, m;
     double r, sum, l, mid, PI;
     int i;

     PI = acos(-);

     scanf("%d", &case_n);

     while (case_n--) {
         scanf("%d %d", &n, &f);
         sum = 0.0f;
         for (i=; i<n; ++i) {
             scanf("%lf", &r);
             areas[i] = PI*r*r;
             sum += areas[i];
         }
         l = 0.0f;
         ++f;
         r = sum/f;
         while (r-l > eps) {
             mid = (l+r)/;
             m = ;
             for (i=; i<n; ++i)
                 m += (int)(areas[i]/mid);
             if (m < f)
                 r = mid;
             else
                 l = mid;
         }
         printf("%.4lf\n", l);
     }

     return ;
 }