模板，注意精度一般为1e-6，1e-8跟1e-10用的较少。
double three_devide(double l, double r)
{
double left = l, right = r,mid,midmid;
while(left + esp < right)
{
mid = (left + right)/2;
midmid = (mid + right)/2;
if(cal(mid) >= cal(midmid))//根据所有是极大值还是极小值变换。
right = midmid;
else
left = mid;
}
return cal(right);
}
Light Bulb
ZOJ - 3203Compared to wildleopard's wealthiness, his brother mildleopard is rather poor. His house is narrow and he has only one light bulb in his house. Every night, he is wandering in his incommodious house, thinking of how to earn more money. One day, he found that the length of his shadow was changing from time to time while walking between the light bulb and the wall of his house. A sudden thought ran through his mind and he wanted to know the maximum length of his shadow.
Input
The first line of the input contains an integer T (T <= 100), indicating the number of cases.
Each test case contains three real numbers H, h and D in one line. H is the height of the light bulb while h is the height of mildleopard. D is distance between the light bulb and the wall. All numbers are in range from 10-2 to 103, both inclusive, and H - h >= 10-2.
Output
For each test case, output the maximum length of mildleopard's shadow in one line, accurate up to three decimal places..
Sample Input
3
2 1 0.5
2 0.5 3
4 3 4
Sample Output
1.000
0.750
4.000
#include <iostream>
#include <cstring>
#include <cstdio>
#include <cmath>
using namespace std;
const double esp = 1e-8;
double H, h, D;
double cal(double x)
{
return ((h- H)*D/x + H + D - x);
}
double three_devide(double l, double r)
{
double left = l, right = r,mid,midmid;
while(left + esp < right)
{
mid = (left + right)/2;
midmid = (mid + right)/2;
if(cal(mid) >= cal(midmid))//=
right = midmid;
else
left = mid;
}
return cal(right);
}
int main()
{
int t;
scanf("%d",&t);
while(t --)
{
scanf("%lf %lf %lf", &H, &h, &D);
double ans = three_devide(D - h*D/H,D);
printf("%.3f\n", ans);
}
return 0;
}