1 /* 2     二分搜索：枚举高度，计算体积与给出的比较。  3 */ 4 #include 
     
       5 #include 
      
        6 #include 
       
         7 #include 
        
          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 Cup24     //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\n", mid);37     }38 39     return 0;40 }