二分搜索 HDOJ 2289 Cup

 1 /*
 2     二分搜索：枚举高度，计算体积与给出的比较。 
 3 */
 4 #include <cstdio>
 5 #include <algorithm>
 6 #include <cstring>
 7 #include <cmath>
 8 using namespace std;
 9 
10 const int MAXN = 1e3 + 10;
11 const int INF = 0x3f3f3f3f;
12 const double EPS = 1e-8;
13 const double PI = acos (-1.0);
14 double r, R, H, V;
15 double x;
16 
17 double cal(double h1)    {
18     double u = r + (R - r) * h1 / H;        //上底
19     double V1 = PI / 3.0 * h1 * (r * r + r * u + u * u);    //圆台计算公式
20     return V1;
21 }
22 
23 int main(void)  {       //HDOJ 2289 Cup
24     //freopen ("HDOJ_2289.in", "r", stdin);
25 
26     int T;  scanf ("%d", &T);
27     while (T--) {
28         scanf ("%lf%lf%lf%lf", &r, &R, &H, &V);
29         double mid;
30         double low = 0, upp = H;
31         while (upp - low > EPS)  {
32             mid = (low + upp) / 2;
33             if (cal (mid) - V > EPS)    upp = mid;
34             else low = mid;
35         }
36         printf ("%.6f
", mid);
37     }
38 
39     return 0;
40 }
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