HDU-5919 Sequence II

HDU-2899 Strange fuction

題目傳送門

求fx=6x7+8x6+7x3+5x2−yx(0<=x<=100) 的最小值。

題目很簡單，三分就好了，但三分很坑啊。

注意

1.三等分點公式

mid1=2head+tail3

mid2=head+2tail3

2.注意刪除調試語句啊233。

代碼

#include<bits/stdc++.h>

using namespace std;
void work();
double cf(double x,double u)
{
    double ans=1;
    for(int i=1;i<=u;i++)
        ans*=x;
    return ans;
}
double fx(double x,double y)
{
    //cout<<x<<" "<<y<<endl;
    double ans=1;
    ans=6*cf(x,7)+8*cf(x,6)+7*cf(x,3)+5*cf(x,2)-y*cf(x,1);
    return ans;
}
int main()
{
    int T;
    cin>>T;
    for(int i=1;i<=T;i++)
        work();
}
void work()
{
    double y;
    cin>>y;
    double tail,mid1,mid2,head;
    head=-0.00001;tail=100.1;
    while(tail-head>0.000001)
    {
        mid1=(2*head+tail)/3;
        mid2=(head+2*tail)/3;
        //cout<<mid1<<" "<<y<<endl;
        double a1=fx(mid1,y),a2=fx(mid2,y);
        //cout<<a1<<" "<<a2<<endl;
        //system("pause");
        if(a1>a2)
            head=mid1;
        else tail=mid2;
    }
    printf("%0.4f\n",fx(head,y));
}