C# Permutation of an array of arraylists?

Question

I have an ArrayList[] myList and I am trying to create a list of all the permutations of the values in the arrays.

EXAMPLE: (all values are strings)

Answer 1

I recently ran across a similar problem in a project of mine and stumbled on this question. I needed a non-recursive solution that could work with lists of arbitrary objects. Here's what I came up with. Basically I'm forming a list of enumerators for each of the sub-lists and incrementing them iteratively.

public static IEnumerable> GetPermutations(IEnumerable> lists)
{
    // Check against an empty list.
    if (!lists.Any())
    {
        yield break;
    }

    // Create a list of iterators into each of the sub-lists.
    List> iterators = new List>();
    foreach (var list in lists)
    {
        var it = list.GetEnumerator();
        // Ensure empty sub-lists are excluded.
        if (!it.MoveNext())
        {
            continue;
        }
        iterators.Add(it);
    }

    bool done = false;
    while (!done)
    {
        // Return the current state of all the iterator, this permutation.
        yield return from it in iterators select it.Current;

        // Move to the next permutation.
        bool recurse = false;
        var mainIt = iterators.GetEnumerator();
        mainIt.MoveNext(); // Move to the first, succeeds; the main list is not empty.
        do
        {
            recurse = false;
            var subIt = mainIt.Current;
            if (!subIt.MoveNext())
            {
                subIt.Reset(); // Note the sub-list must be a reset-able IEnumerable!
                subIt.MoveNext(); // Move to the first, succeeds; each sub-list is not empty.

                if (!mainIt.MoveNext())
                {
                    done = true;
                }
                else
                {
                    recurse = true;
                }
            }
        }
        while (recurse);
    }
}