HDU 2199 Can you solve this equation? (二分 水题)

 

Can you solve this equation?

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

Total Submission(s): 6023    Accepted Submission(s): 2846

 

Problem Description

Now,given the equation 8*x^4 + 7*x^3 + 2*x^2 + 3*x + 6 == Y,can you find its solution between 0 and 100;
Now please try your lucky.

 

 

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 a real number Y (fabs(Y) <= 1e10);

 

 

Output

For each test case, you should just output one real number(accurate up to 4 decimal places),which is the solution of the equation,or “No solution!”,if there is no solution for the equation between 0 and 100.

 

 

Sample Input

2 100 -4

 

 

Sample Output

1.6152 No solution!

 

 

Author

Redow

 

 

 

一道初学者的二分题，讲课用

 

#include <iostream>

#include <cstdio>

using namespace std;



double y;



double getfx(double x){

	return 8*x*x*x*x + 7*x*x*x + 2*x*x + 3*x + 6;

}



void computing(){

	if(getfx(100)<y-1e-3 || getfx(0)>y+1e-3){

		printf("No solution!\n");

		return;

	}

	double l=0,r=100;

	while(r-l>1e-6){

		double mid=(l+r)/2;

		if(getfx(mid)>y) r=mid;

		else l=mid;

	}

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

}



int main(){

	int t;

	scanf("%d",&t);

	while(t-- >0){

		scanf("%lf",&y);

		computing();

	}

	return 0;

}