Question

I have a subroutine:

private static IEnumerable<IEnumerable<T>> permutations<T>(IEnumerable<T> source)
{
    var c = source.Count();
    if (c == 1)
        yield return source;
    else
        for (int i = 0; i < c; i++)
            foreach (var p in permutations(source.Take(i).Concat(source.Skip(i + 1))))
                yield return source.Skip(i).Take(1).Concat(p);
    }

Then how to call it in main function?

static void Main(string[] args)
{
    string input = "abcdefghijk";
    IEnumerable<string> summary;
    summary= permutations<string>(IEnumerable<string> input);// obviously wrong, but how??
}

Answer 1

Calling the function is easy, you just need:

permutations(input)

This will give you a result that is a sequence of characters sequences. To convert the inner IEnumerable<char> into strings just use Select.

summary = permutations(input).Select(chars => new string(chars.ToArray()));