hdu 2199 解方程（二分法）

#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cstring>
#include<cmath>
using namespace std;
double ans,s,t,mid,y;
void solve(double s,double t,double y)
{
    double tmp1,tmp2,mid_2;
     mid= (s+t)/2;
     if(fabs(s-t)<1e-10)
     {ans=mid;return;}
    mid_2=8*(pow(mid,4))+7*(pow(mid,3))+2*(pow(mid,2))+3*mid+6;
    if(mid_2>y)
    solve(s,mid,y);
    else
    solve(mid,t,y);
}
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%lf",&y);
        if(y<6||y>807020306)
        printf("No solution!\n");
        else
        {
              solve(0,100,y);
              printf("%.4lf\n",ans);
        }

    }
    return 0;
}