『算法-ACM 竞赛-』HDU 2199 Can you solve this equation_

Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 29378 Accepted Submission(s): 12331

Problem Description

Now,given the equation 8x^4 + 7x^3 + 2x^2 + 3x + 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

Recommend

lcy

二分水题，多看看就能理解。

#include<iostream>
#include<algorithm>
#include<vector>
#include<cmath>
#include<iomanip>
using namespace std;
double ys(double e)
{
    return 8*pow(e,4)+7*pow(e,3)+2*pow(e,2)+3*e+6;
}
int judge(double u)
{
	double v;
	v=8*pow(100,4)+7*pow(100,3)+2*pow(100,2)+3*100+6;
	if(v>=u&&u>=6)
	return true;
	return false;
}
int main()
{
	int T;
	double n,left,right,node;
	cin>>T;
	while(T--)
	{
		cin>>n;
		if(!judge(n))
		cout<<"No solution!"<<endl;
		else
		{
			left=0;right=100;
			while(right-left>0.000001)
			{
				node=(left+right)/2;
				if(ys(node)>n)
				right=node;
				else
				left=node;
			}
			cout<<fixed<<setprecision(4)<<node<<endl;
		}
	}
}