private IEnumerable <string> EnumerateWords(IEnumerable <Letter> letters, WordBuilder builder)
{
foreach (Letter letter in letters)
{
// Only continue with this letter if the prefix exists
if (Trie.Matcher.HasNext(letter.C))
{
// Add the current letter to the prefix
Trie.Matcher.Next(letter.C);
// If the current prefix is a word, capture it
if (Trie.Matcher.IsMatch())
{
string word = Trie.Matcher.PrefixMatched;
yield return(word);
}
// Create a new word builder to descend with
WordBuilder nextBuilder = new WordBuilder(builder);
nextBuilder.AddLetter(letter);
// Get adjacent letters that haven't already been used in this word
IEnumerable <Letter> nextLetters = letter.AdjacentLetters.Where(x => !nextBuilder.UsedLetters.Contains(x));
// Descend into the adjacent letters
foreach (string word in EnumerateWords(nextLetters, nextBuilder))
{
yield return(word);
}
// Remove the current letter from the prefix
Trie.Matcher.Back();
}
}
}
private IEnumerable <string> EnumerateWords(BoggleBoard boggleBoard)
{
// Create structure to manage adjacent letters
Board board = CreateBoard(boggleBoard);
// Find all the words
WordBuilder builder = new WordBuilder();
foreach (string word in EnumerateWords(board.Letters, builder))
{
yield return(word);
}
}
public WordBuilder(WordBuilder builder)
{
// Copy the items, but not a deep copy
UsedLetters = new HashSet <Letter>(builder.UsedLetters);
}