Question

For input text like “A.B.C.D. EFG”, I would like to get permutations of letters followed by dots to be converted to add space after the dot. So for the example above, I would like to get “A.B.C.D.”, “A. B.C.D.”, “A.B. C.D.”, “A.B.C. D.”, “A. B. C.D.”, “A.B. C. D.”, “A. B. C. D.”

Can this be done with regex ? If yes then any regex sample that works with c# (.net) would be most appreciated. The number of characters with dots is not known and can vary from text to text.

On a side note, if the text is “A. B. C. D. EFG” or “A. B.C.D. EFG” etc, I would like to get all permutations for that.

Regards

Answer 1

Something like

static string[] GetPermutations(string input)
{
    List<string> ret = new List<string>();
    List<string> cleanInput = new List<string>();
    foreach (string bit in input.Split('.'))
    {
        if (bit.Trim().Length > 0) cleanInput.Add(bit.Trim());
    }
    foreach (string bit in cleanInput)
    {
        if (ret.Count == 0)
        {
            ret.Add(bit);
            continue;
        }
        List<string> oldRet = ret;
        ret = new List<string>();
        foreach (string oldBit in oldRet)
        {
            ret.Add(oldBit + bit);
            ret.Add(oldBit + " " + bit);
        }
    }
    return ret.ToArray();
}

Then, to call it:-

foreach (string p in GetPermutations("A.B. C.D."))
{
    Console.WriteLine(p);
}

It outputs:-

ABCD
ABC D
AB CD
AB C D
A BCD
A BC D
A B CD
A B C D

You just need to add the dots in, and check any other unspecified logic you may need (eg, stripping away the EFG’s from your example input.