【HDOJ】1969 Pie

二分。
 1 #include <stdio.h>
 2 #include <math.h>
 3 
 4 const double eps = 1e-6;
 5 double areas[10001];
 6 
 7 int main() {
 8     int case_n, n, f, m;
 9     double r, sum, l, mid, PI;
10     int i;
11 
12     PI = acos(-1);
13 
14     scanf("%d", &case_n);
15 
16     while (case_n--) {
17         scanf("%d %d", &n, &f);
18         sum = 0.0f;
19         for (i=0; i<n; ++i) {
20             scanf("%lf", &r);
21             areas[i] = PI*r*r;
22             sum += areas[i];
23         }
24         l = 0.0f;
25         ++f;
26         r = sum/f;
27         while (r-l > eps) {
28             mid = (l+r)/2;
29             m = 0;
30             for (i=0; i<n; ++i)
31                 m += (int)(areas[i]/mid);
32             if (m < f)
33                 r = mid;
34             else
35                 l = mid;
36         }
37         printf("%.4lf
", l);
38     }
39 
40     return 0;
41 }