hdu 2199 Can you solve this equation? 二分

 

/*
 * hdu2199.c
 *
 *  Created on: 2011-10-9
 *      Author: bjfuwangzhu
 */

#include<stdio.h>
#include<math.h>
#define eps 1.0e-10
double f(double x) {
    return 8.0 * pow(x, 4.0) + 7.0 * pow(x, 3.0) + 2.0 * pow(x, 2.0) + 3 * x + 6;
}
void solve(double y) {
    double left, right, mid;
    left = 0.0, right = 100.0;
    if (f(left) > y || f(right) < y) {
        puts("No solution!");
    } else {
        while (fabs(left - right) > eps) {
            mid = (left + right) / 2;
            if (f(mid) > y) {
                right = mid;
            } else {
                left = mid;
            }
        }
        printf("%.4lf\n", mid);
    }
}
int main() {
#ifndef ONLINE_JUDGE
    freopen("data.in", "r", stdin);
#endif
    int t;
    double y;
    scanf("%d", &t);
    while (t--) {
        scanf("%lf", &y);
        solve(y);
    }
    return 0;
}