一元三次方程

#include 
#include 
#include 
using namespace std;
double a,b,c,d,f,ans[4];
int n;
double sum(double x)
{
    return a*x*x*x+b*x*x+c*x+d;
}
void erfen(double head,double tail)
{
    if(sum(head)*sum(tail)>0 && ((tail-head)<1 || n>=2))
        return ;
    double mid=(head+tail)/2;
    if(sum(mid)<=1e-4 && sum(mid)>=-1e-4)
    {
         ans[++n]=mid;
         mid++;
         return;
    } 
    erfen(head,mid),erfen(mid,tail);
}
int main()
{
     cin>>a>>b>>c>>d;
     erfen(-100,100);
     cout<<fixed<2)<1]<<" "<2]<<" "<3];
}