HDU 2899 Strange fuction [二分]

1.题意：给一个函数F（X）的表达式，求其最值，自变量定义域为0到100

2.分析：写出题面函数的导函数的表达式，二分求导函数的零点，对应的就是极值点

3.代码：

 # include <iostream>
 # include <cstdio>
 # include <cmath>
 using namespace std;
 const double eps=1e-;
 double Y;
 int sgn(double x)
 {
     if(fabs(x)<eps) return ;
     if(x>) return ;
     else return -;
 }
 double F(double x)
 {
     return 6.0*pow(x,)+8.0*pow(x,)+7.0*pow(x,)+5.0*pow(x,)-Y*x;
 }
 double f(double x)
 {
     return 42.0*pow(x,)+48.0*pow(x,)+21.0*pow(x,)+10.0*x-Y;
 }
 void Solve()
 {
     scanf("%lf",&Y);
     double l=;
     double r=;
     while(r-l>eps)
     {
         double mid=l+(r-l)/2.0;
         if(sgn(f(mid))>) r=mid;
         else l=mid;
     }
     printf("%.4f\n",F(l));
 }
 int main()
 {
     int T;
     scanf("%d",&T);
     while(T--)
     {
         Solve();
     }
     return ;
 }