c++ set<int>::iterator j

#include <iostream>
#include <vector>
#include <set>
using namespace std;

int main(){
    int a[6]={-4,-1,-1,0,1,2};
    int i,j,k;
    set<int> S;
    set<int>::iterator it;
    for(i=0;i<6;i++)
        for(j=i+1;j<6;j++){
            for(k=j+1;k<6;k++){
                if(a[i]+a[j]+a[k]==0)
                    break;
                if(k<5&&(a[i]+a[j]+a[k]<0)&&(a[i]+a[j]+a[k]>0))
                    break;
            }
            if(a[i]+a[j]+a[k]==0){
                int key=100*a[i]+10*a[j]+a[k];
                if(S.empty()){
                    cout<<a[i]<<" "<<a[j]<<" "<<a[k]<<endl;
                    S.insert(key);
                }
                else{
                    for(it=S.begin();it!=S.end();it++){
                        if(*it==key)
                            break;
                    }
                    if(it==S.end()){
                        S.insert(key);
                        cout<<a[i]<<" "<<a[j]<<" "<<a[k]<<endl;
                    }
                }
            }
        }
}