HDU 2289 Cup

Cup

Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 8887    Accepted Submission(s): 2720

Problem Description

The WHU ACM Team has a big cup, with which every member drinks water. Now, we know the volume of the water in the cup, can you tell us it height?

The radius of the cup's top and bottom circle is known, the cup's height is also known.

 

 

Input

The input consists of several test cases. The first line of input contains an integer T, indicating the num of test cases.
Each test case is on a single line, and it consists of four floating point numbers: r, R, H, V, representing the bottom radius, the top radius, the height and the volume of the hot water.
Technical Specification
1. T ≤ 20.
2. 1 ≤ r, R, H ≤ 100; 0 ≤ V ≤ 1000,000,000.
3. r ≤ R.
4. r, R, H, V are separated by ONE whitespace.
5. There is NO empty line between two neighboring cases.

Output

For each test case, output the height of hot water on a single line. Please round it to six fractional digits.

 

Sample Input

1 100 100 100 3141562

Sample Output

99.999024

二分搜索
注意体积圆台公式v=h*(R*R+r*r+R*r)*π/3；

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <algorithm>
using namespace std;
typedef long long ll;
#define mod 1e-8
#define p 3.1415926535
double r,R,H,V;
int t;
double check(double r,double R,double h,double H)
{
    double x=h/H*(R-r)+r;  
    return (p*(r*r+x*x+r*x)*h)/3.0; 
}
int main()
{
    scanf("%d",&t);
    while(t--)
    {
        scanf("%lf%lf%lf%lf",&r,&R,&H,&V);
        double lh=0,rh=100,mid;
        while((rh-lh)>mod)
        {
            mid=(lh+rh)/2;
            double xx=check(r,R,mid,H);
            if(xx<V){
                lh=mid;
            }
            else rh=mid;
        }
        printf("%.6lf\n",mid);
    }
    return 0;
}