list the possible anagrams of a given string and use the result to create a regular expression in csharp

main.cs
public static List<string> GetAnagrams(string input)
{
    var anagrams = new List<string>();

    // base case: anagrams of a one-character string is the string itself
    if (input.Length == 1)
    {
        anagrams.Add(input);
    }
    else
    {
        // iterate through each character in the input string
        for (int i = 0; i < input.Length; i++)
        {
            // get the character at the current index
            char c = input[i];

            // get the remaining characters in the input string, excluding the current one
            string remaining = input.Substring(0, i) + input.Substring(i + 1);

            // recursively generate anagrams of the remaining characters
            List<string> subAnagrams = GetAnagrams(remaining);

            // iterate through each sub-anagram and add the current character to each position
            foreach (string sub in subAnagrams)
            {
                anagrams.Add(c + sub);
            }
        }
    }

    return anagrams;
}
1015 chars
34 lines

main.cs
public static string GenerateAnagramRegex(string input)
{
    // get all possible anagrams
    List<string> anagrams = GetAnagrams(input);

    // join the anagrams with the regex OR operator (|)
    string regex = string.Join("|", anagrams);

    // add word boundary matchers to the beginning and end of the regex to ensure exact matches
    regex = @"\b(" + regex + @")\b";

    return regex;
}
398 chars
14 lines