Permutations II

Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example, [1,1,2] have the following unique permutations: [1,1,2], [1,2,1], and [2,1,1].

vector<vector<int> >& permute(vector<int> vecInt)
{
    vector<int> vecWorker;
    vector<vector<int> > vecPermu;
    vector<int> vecVisit(vecInt.size());

    sort(vecInt.begin(), vecInt.end());
    
    helper(vecPermu, vecWorker, vecInt, vecVisit);

    return vecPermu;
}

void helper(vector<vector<int> >& vecPermu, vector<int>& vecWorker, const vector<int>& vecInt, vector<int>& vecVisit)
{
    if (vecWorker.size() == vecInt.size())
    {
        vecPermu.push_back(vecWorker);
        return;
    }

    for (int i = 0; i < vecInt.size(); i++)
    {
        if (vecVisit[i] == 1 || (i != 0 && vecInt[i] == vecInt[i-1] && vecVisit[i-1] == 0))
        {
            continue;
        }

        vecVisit[i] = 1;
        vecWorker.push_back(vecInt[i];
        helper(vecPermu, vecWorker, vecInt);
        vecWorker.pop_back(vecInt[i]);
        vecVisit[i] = 0;
    }
}