链接：

细节问题：

1、r为下底，R为上底，r<=R

2、v==0直接输出"0"

3、ans>h直接输出h

4、圆台体积公式：PI*h*(r*r+r*R+R*R) / 3; 

 1 #include <cstdio>

 2 #include <cmath>

 3 

#define PI (double)acos(-1.0)

 4 

 5 

int main()

 6 {

 7     

int t;

 8     

double r1,r2,h,v,x,r3,vv,left,right,y;

 9     scanf(

"

%d

",&t);

10     

while(t--)

11     {

12         scanf(

"

%lf%lf%lf%lf

",&r1,&r2,&h,&v);

13         

if(v<1e-

12)

14             printf(

"

0.000000\n

");

15         

else 

if((r2-r1)<1e-

12)

16         {

17             

double ans = v / (r1 * r1 * PI);

18             

if(ans>h)

19                 printf(

"

%.6lf\n

",h);

20             

else

21                 printf(

"

%.6lf\n

",ans);

22         }

23         

else

24         {

25             left = 

0; right = h;

26             

while(right-left>1e-

12)

27             {

28                 y = (left + right) / 

2;

29                 r3 = r1 + (r2 - r1) * y / h;

30                 vv = PI * y * (r3*r3 + r1*r1 + r1*r3) / 

3;

31                 

if(vv>v)

32                     right = y;

33                 

else

34                     left = y;

35             }

36             printf(

"

%.6lf\n

",y);

37         }

38     }

39     

return 

0;

40 }