Strange fuction

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)

Total Submission(s): 2982 Accepted Submission(s): 2202

Problem Description

Now, here is a fuction:

F(x) = 6 * x^7+8*x^6+7*x^3+5*x^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

Sample Output

-74.4291

-178.8534

#include <stdio.h>

#include <math.h>

double y, ans;

double f(double x){

	return 6 * pow(x, 7) + 8 * pow(x, 6) +

		7 * pow(x, 3) + 5 * x * x - y * x;

}

double ff(double x){ //求导

	return 42 * pow(x, 6) + 48 * pow(x, 5)

		+ 21 * x * x + 10 * x - y;

}

int main(){

	int n;

	scanf("%d", &n);

	while(n--){

		scanf("%lf", &y);

		if(ff(0) >= 0) ans = f(0);

		else if(ff(100) <= 0) ans = f(100);

		else{

			double left = 0, right = 100, mid;

			while(left + 1e-8 < right){

				mid = (left + right) / 2;

				if(ff(mid) > 0) right = mid;

				else if(ff(mid) < 0) left = mid;

				else break;

			}

			ans = f(mid);

		}

		printf("%.4lf\n", ans);

	}

	return 0;

}

巴特西

HDU2899 Strange fuction 【二分】

Strange fuction

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