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  • HDU 2899 Strange fuction

    Strange fuction
    Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
    Total Submission(s): 11746 Accepted Submission(s): 7841

    Problem Description
    Now, here is a fuction:
    F(x) = 6 * x^7 +8* x^6 + 7x^ 3+5x^2-y*x (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

    Author
    Redow

    Recommend
    lcy

    这个题可以三分求单调性,也可以求导再进行计算。

    #include<iostream>
    #include<cstdio>
    using namespace std;
    double F(double x,double y)
    {
    	return 6*pow(x,7)+8*pow(x,6)+7*pow(x,3)+5*pow(x,2)-y*x;
    }
    double f(double x)//易知导函数单调递增,则原函数先减后增;
    {
    	return 42*pow(x,6)+48*pow(x,5)+21*pow(x,2)+10*x;
    }
    int main()
    {
    	int t;
    	double y,l,h,mid;
    	cin>>t;
    	while(t--)
    	{
    		cin>>y;
    		l=0.0;h=100.0;
    		while(h-l>1e-7)
    		{
    			mid=(l+h)/2;
    			if(f(mid)<y) l=mid;
    			else h=mid;
    		}
    		printf ("%.4lf
    ",F(mid,y));
    
    	}
    	return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/lunatic-talent/p/12798936.html
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