二分搜索 （高精度）

HDU 2199

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cctype>
#include<cmath>
#include<algorithm>
using namespace std;

#define N 510
#define INF 0x3f3f3f3f
#define MIN 0.00000001
#define s 0.0000001
typedef long long LL;

int a[N], b[N], c[N], sum[N*N];

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


int main()
{
    int T;
    double y;
    scanf("%d", &T);

    while(T--)
    {
        scanf("%lf", &y);
        double l, r, mid;
        l=0, r=100;
        if(js(0)>y || js(100)<y)
            printf("No solution!
");
        else
        {
            while(r-l>s)
            {
                mid=(l+r)/2;
                if(js(mid)>y)
                    r=mid+MIN;
                else if(js(mid)<y)
                    l=mid-MIN;
            }
            printf("%.4f
", (l+r)/2);
        }
    }
    return 0;
}