/// <summary>
        /// Calculates the priority based on the frequency that the character changed to in the candidate word is the 'changed from' character in a substitution between adjacent words.
        /// </summary>
        /// <param name="currentWord">The current word being traversed from.</param>
        /// <param name="candidateWord">The candidate word to calculate the priority for.</param>
        /// <param name="destinationWord">The destination word.</param>
        /// <param name="distanceFromSourceToCandidateWord">The distance (in graph edges) from the source word, to the candidate word.</param>
        /// <returns>The priority.</returns>
        protected Double CalculatePopularityOfChangeToCharacterPriority(String currentWord, String candidateWord, String destinationWord, Int32 distanceFromSourceToCandidateWord)
        {
            Char  changeToCharacter      = wordUtilities.FindDifferingCharacters(currentWord, candidateWord).Item2;
            Int32 fromCharacterFrequency = fromCharacterFrequencies.GetFrequency(changeToCharacter);

            return(1.0 - (Convert.ToDouble(fromCharacterFrequency) / Convert.ToDouble(maximumFromCharacterFrequency)));
        }
        /// <summary>
        /// Reads a set of words from a stream, and adds the words and statistics pertaining to the words to a set of data structures.
        /// </summary>
        /// <param name="reader">The stream reader to used to read the set of words (allows specifying a mocked reader for unit testing).</param>
        /// <param name="trieBuilder">The trie builder to use to add the words to the trie (allows specifying a mocked builder for unit testing).</param>
        /// <param name="wordFilterFunction">A Func to filter whether or not the specified word should be added to the trie.  Accepts the word as a parameter, and returns a bookean indicating whether that word should be added to the trie.</param>
        /// <param name="allWordsTrieRoot">The root of a character trie to populate with the words.</param>
        /// <param name="allWords">A HashSet to populate with the words.</param>
        /// <param name="fromCharacterFrequencies">A FrequencyTable to populate with the number of times each character is the 'from' character in a substitution.</param>
        /// <param name="characterSubstitutionFrequencies">A FrequencyTable to populate with the number of times each pair of characters in a substitution occur.</param>
        public void PopulateAdjacentWordDataStructures(IStreamReader reader, ICharacterTrieBuilder trieBuilder, Func <String, Boolean> wordFilterFunction, Dictionary <Char, TrieNode <Char> > allWordsTrieRoot, HashSet <String> allWords, FrequencyTable <Char> fromCharacterFrequencies, FrequencyTable <CharacterSubstitution> characterSubstitutionFrequencies)
        {
            // Read all words and add them to the HashSet and trie
            using (reader)
            {
                while (reader.EndOfStream == false)
                {
                    String currentWord = reader.ReadLine();
                    if (wordFilterFunction.Invoke(currentWord) == true)
                    {
                        if (allWords.Contains(currentWord) == false)
                        {
                            allWords.Add(currentWord);
                            trieBuilder.AddWord(allWordsTrieRoot, currentWord, true);
                        }
                    }
                }
            }

            // Populate the frequency tables
            CharacterTrieUtilities trieUtilities = new CharacterTrieUtilities();
            WordUtilities          wordUtilities = new WordUtilities();

            foreach (String currentWord in allWords)
            {
                foreach (String adjacentWord in trieUtilities.FindAdjacentWords(allWordsTrieRoot, currentWord))
                {
                    // Find the character which was substitued between the word and the adjacent word
                    Tuple <Char, Char> differingCharacters = wordUtilities.FindDifferingCharacters(currentWord, adjacentWord);
                    Char fromCharacter = differingCharacters.Item1, toCharacter = differingCharacters.Item2;

                    // Increment the data structures
                    fromCharacterFrequencies.Increment(fromCharacter);
                    characterSubstitutionFrequencies.Increment(new CharacterSubstitution(fromCharacter, toCharacter));
                }
            }
        }