Day3-K-Can you solve this equation? HDU2199

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.

InputThe 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);OutputFor 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!

思路：二分查找答案问题，设置精度后直接查找即可，代码如下：

double Y;

double check(double x) {
    return 8 * (x * x * x * x) + 7 * (x * x * x) + 2 * (x * x) + 3 * x + 6;
}

int main() {
    int T;
    scanf("%d", &T);
    while(T--) {
        double l = 0.0, r = 100.0, mid;
        scanf("%lf", &Y);
        if(check(0.0) > Y || check(100.0) < Y) {
            printf("No solution!\n");
            continue;
        }
        while(r - l > 1e-10) {
            mid = (r + l) / 2.0;
            if(check(mid) - Y > 0)
                r = mid;
            else
                l = mid;
        }
        printf("%.4lf\n", mid);
    }
    return 0;
}

View Code