hunnu 10922 二分答案

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;
input a y,seach for the x suit for this function

 

 

#include <stdio.h>
#include <math.h>

#define EPS 1e-6
double f(double x)
{
    double res = 6.0,t = x;
    res +=3 *t;
    t *= x;
    res += 2 * t;
    t *= x;
    res += 7 * t;
    t *= x;
    res += 8 * t;
    return res;
}
int main()
{
    double y,low = f(0.0) ,high = f(100.0);
    int t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%lf",&y);
        if(y < low || y > high)
        {
            printf("Nosolution!\n");
            continue;
        }
        double l = 0.0, r = 100.0,mid,res;
        while(l < r)
        {
            mid = (l + r)/2.0;
            res = f(mid)-y;
            if(fabs(res) < EPS)
                break;
            if(res > 0.0)
                r = mid;
            else
                l = mid;
        }
        printf("%.4lf\n",mid);
    }
    return 0;
}