给定C++快速排序代码，选出错误的返回表达式

vector<int> operator +(vector<int> lA, vector<int> lB)
{
    vector<int> lst;
    for (int i = 1; i < lA.size(); i++)
        lst.push_back(lA[i]);
    for (int i = 1; i < lB.size(); i++)
        lst.push_back(lB[i]);
    return lst;
}
vector<int> qSort(vector<int> lst)
{
    if (lst.size() < 2)
        return lst;
    int pivot = lst[0];
    vector<int> less, greater;
    for (int i = 1; i < lst.size(); i++)
        if (lst[i] <= pivot) less.push_back(lst[i]);
        else greater.push_back(lst[i]);
    return ____________________;
}