为什么这样写特别容易重复？如何去除重复？？？？？？？？？

#include<iostream>
#include<vector>
#include<cmath>
#include<iomanip>
using namespace std;
double a,b,c,d;
double equation(double x){
    return a*x*x*x+b*x*x+c*x+d;
}
int main(){
    cin>>a>>b>>c>>d;
    vector<double>solve;
    for(int i=-100;i<100;i++){
        double left=i,right=i+1;
        while(equation(left)*equation(right)<=0&&right-left>10e-4){
            //cout<<"left="<<left<<"     right="<<right<<endl;
            if(fabs(equation(left))<=10e-3){
                solve.push_back(left);
                break;
            }
            double mid=(left+right)/2;
            if(equation(mid)*equation(left)>0){
                break;
            }
            else{
                right=mid;
            }
        }
    }
    //cout<<solve.size()<<endl;
    for(int i=0;i<solve.size();i++){
        cout<<fixed<<setprecision(2)<<solve[i]<<" ";
    }
    return 0;
}