一本通例题

#include <bits/stdc++.h>
using namespace std;

double fn(double x,double a,double b,double c,double d);

int main()
{
    double a,b,c,d;
    cin >>a>>b>>c>>d;
    for(int i=-10000; i<=10000; i++){
        double x1=(i-0.05)/100;
        double x2=(i+0.05)/100;
        if(fn(x1,a,b,c,d)*fn(x2,a,b,c,d)<0 || fn(x1,a,b,c,d)==0){
            printf("%.2f",double(i)/100);
            cout <<" ";
        }
    }



    return 0;
}
    double fn(double x,double a,double b,double c,double d){
        double f;
        f=a*x*x*x+b*x*x+c*x+d;
        return f;
    }