increasing QList<QStringList> index elements twice

Question

In my Qt C++ application I have a QList I want to increase the contents of each index by the same amount!

void MainWindow::on_pushButton_clicked()
    {

        list1<<"a"<<"b"<<"c"<<"d"<<"e";
        list2<<"f"<<"g"<<"h"<<"i"<<"j";

        List1<<list1;
        List2<<list2;



            for(int k=0;k<2;k++){
            for(int i=0;i<List1.size();i++){
                for(int j=0;j<List1[0].size();j++){
                List1[i]<<List1[i][j];
                }
            }

    }
    }

from the above code I want to make the contents of 0th index of List (i.e List[0]) a QStringList of "a" "b" "c" "d" "e" "a" "b" "c" "d" "e" and the contents of 1st index of List (i.e List[1]) a QStringList of "f" "g" "h" "i" "j" "f" "g" "h" "i" "j"! But when I click the button I get the run time error stating

terminate called after throwing an instance of 'std::bad_alloc'

How can I correct this?

Answer 1

In case you have problems with code, try to make it work as a complete sample, like this:

void test()
{
    QList<QStringList> ListOfLists;

    ListOfLists.append(QStringList());
    ListOfLists.append(QStringList());

    ListOfLists[0] << "a" << "b";
    ListOfLists[1] << "g" << "f";

    qDebug() << ListOfLists; // (("a", "b"), ("g", "f"))

    for (int i=0; i<ListOfLists.size(); ++i)
    {
        QStringList tempList = ListOfLists[i];

        foreach(QString s, tempList)
        {
            ListOfLists[i] << s;
        }
    }

    qDebug() << ListOfLists; // (("a", "b", "a", "b"), ("g", "f", "g", "f"))
}

Usually, problems disappear, once you rewrite your code in clean way. Your code has two Lists, List1 and List2 and some array, where nobody can track what goes wrong. I quess, that your code recurses over the list until memory is exhausted. That's why I make a copy called tempList to avoid infinite recursion.