VJudge--Strange fuction

题目 - Strange fuction

Now, here is a fuction:
F(x) = 6 * x^7+8x^6+7x^3+5x^2-yx (0 <= x <=100)
Can you find the minimum value when x is between 0 and 100.

Input

The first line of the input contains an integer T(1<=T<=100) which means the number of test cases. Then T lines follow, each line has only one real numbers Y.(0 < Y <1e10)

Output

Just the minimum value (accurate up to 4 decimal places),when x is between 0 and 100.

Sample Input

2
100
200

Sample Output

-74.4291
-178.8534

题意：

​ 输入y的值，大致估算该函数的最小值

AC代码：

#include<iostream>
#include<iomanip>
#include<queue>
#include<cmath>
#include<algorithm>

using namespace std;

const double eps=1e-8; 

double y;

int dir[2]={1,-1};

double f(double x)
{
	return  6*pow(x,7) + 8*pow(x,6) + 7*pow(x,3) + 5*pow(x,2) - y*x;
} 

double anneal()
{
	double T=100;
	double delta=0.98; 
	double x=50.0;
	double now=f(x);
	double ans=now;
	while(T>eps)
	{
		double nowx=x+dir[rand()%2]*T;
		if(nowx>=0.0 && nowx<=100.0)
		{
			now=f(nowx);
			if(ans-now>eps)
			{
				ans=now;
				x=nowx;
			}
		} 
		T*=delta;
	} 
	return ans;
}

int main()
{
	int i,j;
	int t;
	scanf("%d",&t);
	while(t--)
	{
		scanf("%lf",&y);
		printf("%.4lf\n",anneal());
	}
	return 0;
}