Can you solve this equation? （HDU-2199）二分查找

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!

题意：给你方程和y，让你求在0-100中有没有解。

思路：典型的二分查找，设l=0，r=100，套用二分模板，注意精度，这道题就ok了。

AC代码：

#include <bits/stdc++.h>
typedef long long ll;
const int maxx=1010;
const int inf=0x3f3f3f3f;
using namespace std;
double f(double x)
{
    return 8*pow(x,4.0)+7*pow(x,3.0)+2*pow(x,2.0)+3*x+6;
}
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        double y;
        double l,r,mid;
        scanf("%lf",&y);
        l=0;
        r=100;
        if(f(l)<=y && y<=f(r))
        {
            while(r-l>1e-6)
            {
                mid=(l+r)/2;
                double ans=f(mid);
                if(ans>y)
                {
                    r=mid-1e-7;
                }
                else
                    l=mid+1e-7;
            }
            printf("%.4lf\n",mid);
        }
        else
            printf("No solution!\n");
    }
    return 0;
}