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HDU 2199 Can you solve this equation?(二分)

2017-08-10 21:35 316 查看

Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1345 Accepted Submission(s): 633
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
 

Recommend

lcy

#include<iostream>
#include<string>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;

double y;

bool c(double x)
{
double t;
t = 8 * x*x*x*x + 7 * x*x*x + 2 * x*x + 3 * x + 6;
if (t < y)return true;
else return false;
}

int main()
{
int t;
cin >> t;
while (t--)
{

cin >> y;
if (y < 6 || y>807020306) //Y不在0和100之间
{
cout << "No solution!" << endl; continue;
}
double first=0.0;
double last=100.0;
double mid;
for (int i = 0; i < 100; i++)//答案精度管够
{
mid = (first + last) / 2;
if (c(mid))first = mid;//小了在右边
else last = mid;//大于等于在左边
}

printf("%.4lf\n", last);
}
return 0;
}
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