using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        foreach (string[] anagramArray in MyLittleAnagramerV4.FindAnagrams("top", "read", "act", "dear", "spot", "cat", "dare", "stop"))

        {

            Console.WriteLine(string.Join(", ", anagramArray));

        }   

    }

}

public class MyLittleAnagramerV4

{

    public static IEnumerable<IEnumerable<string>> FindAnagrams(params string[] words)

    {

        var cache = new List<HashSet<char>>();

        foreach (var word in words)

        {

            var set = new HashSet<char>(word.ToLower());

            cache.Add(set);

        }

​

        var results = new List<IEnumerable<string>>(words.Length / 2);

​

        int processedWordIndexes = 0;

​

        for (int wordIndex = 0; wordIndex < words.Length; wordIndex++)

        {

            if ((processedWordIndexes & (1 << wordIndex)) != 0)

                continue;

​

            var word = cache[wordIndex];

            processedWordIndexes |= 1 << wordIndex;

​

            var wordAnagramIndexes = 0;

            var wordAnagramCount = 0;

            for (int wordToCompareIndex = wordIndex; wordToCompareIndex < words.Length; wordToCompareIndex++)

            {

                var wordToCompare = cache[wordToCompareIndex];

                if (IsAnagram(word, wordToCompare))

                {

                    wordAnagramIndexes |= 1 << wordToCompareIndex;

                    wordAnagramCount++;

​

                    if (wordIndex != wordToCompareIndex)

                    {

                        processedWordIndexes |= 1 << wordToCompareIndex;

                    }

                }

            }

​

            var wordAnagrams = new string[wordAnagramCount];

​

            for (int wordAnagramIndex = 0, count = 0; count < wordAnagramCount && wordAnagramIndex < int.MaxValue; wordAnagramIndex++)

            {

                if ((wordAnagramIndexes & (1 << wordAnagramIndex)) != 0)

                {

                    wordAnagrams[count] = words[wordAnagramIndex];

                    count++;

                }

            }

​

            results.Add(wordAnagrams);

        }

​

        return results;

    }

​

    public static bool IsAnagram(HashSet<char> left, HashSet<char> right)

    {

        if(left.Count != right.Count)

            return false;

​

        foreach(var @char in left)

        {

            if(!right.Contains(@char))

                return false;

        }

​

        return true;

    }

}