【HDOJ】2289 Cup

二分。另外，圆台体积为v = PI*(r*r+r*R+R*R)*H/3。注意精度。

 1 #include <cstdio>
 2 #include <cmath>
 3 
 4 #define exp 1e-9
 5 
 6 const double PI = acos(-1.0);
 7 
 8 int main() {
 9     int t;
10     double r, R, H, v, lf, rt, mid, r0, nv;
11     scanf("%d", &t);
12 
13     while (t--) {
14         scanf("%lf%lf%lf%lf", &r, &R, &H, &v);
15         lf = 0;
16         rt = H;
17         while (rt >= lf+exp) {
18             mid = (lf+rt)/2;
19             r0 = mid*(R-r)/H+r;
20             nv = PI*(r*r+r*r0+r0*r0)*mid/3;
21             if (fabs(nv -v) <= exp)
22                 break;
23             if (nv < v)
24                 lf = mid;
25             else
26                 rt = mid;
27         }
28         printf("%.6lf
", mid);
29     }
30 
31     return 0;
32 }