1.HDU2199：Can you solve this equation?(二分)
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!
#include "stdafx.h"
#include <iostream>
#include <iomanip>
using namespace std;
int a(double x)
{
return 8 * x*x*x*x + 7 * x*x*x + 2 * x*x + 3 * x + 6;
}
int main()
{
int t = 0;
cin >> t;
while (t--)
{
double n;
cin >> n;
double low = 0.0, high = 100.0;
double mid = (low + high) / 2;
if (a(0) > n || a(100) < n) // 0-100最小值大于n和最大值小于n时无解
{
cout << "No Solution!" << endl;
continue;
}
while (fabs(a(mid) - n) > 0.00001) //解的值带进去得出的结果相差必须小于0.00001循环结束
{
if (a(mid) > n)
high = mid;
else
low = mid;
mid = (low + high) / 2;
}
cout << setprecision(5) << mid << endl;
}
return 0;
}