（HDU）2899 -- Strange fuction （奇怪的功能）

题目链接：https://vjudge.net/problem/HDU-2899

三分搜索例题

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <cmath>
 4 #include <iostream>
 5 #include <algorithm>
 6 #include <string>
 7 #include <cstdlib>
 8 
 9 using namespace std;
10 
11 double fx(double x,double y)
12 {
13     return 6*pow(x,7.0)+8*pow(x,6.0)+7*pow(x,3.0)+5*pow(x,2.0)-y*x;
14 }
15 
16 double bottom,top,mid;
17 
18 int main()
19 {
20     double  y;
21     int T;
22     double liftthird,rightthird;
23     scanf("%d",&T);
24     while(T--)
25     {
26         scanf("%lf",&y);
27         bottom=0;
28         top=100;
29         while(top-bottom>1e-6)
30         {
31             liftthird=(2*bottom+top)/3;
32             rightthird=(bottom+top*2)/3;
33             if(fx(liftthird,y)<fx(rightthird,y)) top=rightthird-1e-7;
34             else bottom=liftthird-1e-7;
35         }
36         printf("%.4lf
",fx((bottom+top)/2,y));
37     }
38     return 0;
39 }