/// <summary>
/// Finds all permutations of chars that form multiword
/// anagrams when the first word is prefixed by wordPrefix.
/// For each of these permutations, adds the words in phrasePrefix
/// appended by the permutation to StringSet, with the word order
/// reversed.
/// </summary>
/// <param name="phrasePrefix">The phrase to prefix
/// each anagram with.</param>
/// <param name="wordPrefix">The string to include as
/// the prefix for the first word in each anagram.</param>
/// <param name="chars">The characters for which to find
/// anagrams.</param>
private ImmutableTrie FindAnagrams(ITrie lastWord, Queue<char> chars)
{
if (lastWord == null)
return null;
ImmutableTrie[] tries = new ImmutableTrie[_map.CharacterCount];
bool nonNull = false;
if (chars.Count == 0)
{
if (lastWord.IsEmpty())
{
Key k = new Key(chars, _map);
ImmutableTrie result = null;
if (_dictionary.TryGetValue(k, out result))
{
tries[_map.GetLocation(' ')] = result;
}
else
{
tries[_map.GetLocation(' ')] = new ImmutableTrie(new ImmutableTrie[0], true, _map);
_dictionary.Add(k, tries[_map.GetLocation(' ')]);
}
if(tries[_map.GetLocation(' ')] != null)
nonNull = true;
}
else //if (prefix.Length == 0)
return null;
//_anagrams.Add("");
}
else
{
if (lastWord.IsEmpty())
{
//char x = chars.Dequeue();
tries[_map.GetLocation(' ')] = FindAnagrams(trie, chars);
if (tries[_map.GetLocation(' ')] != null)
nonNull = true;
//chars.Enqueue(x);
//tries[_map.GetLocation(' ')] = new ImmutableTrie(new ImmutableTrie[0], true, _map);
}
char c = 'Z';
for (int i = 0; i < chars.Count; i++)
{
//if (c == chars.Peek())
// continue;
c = chars.Dequeue();
tries[_map.GetLocation(c)] = FindAnagrams(lastWord.Continuations(c), chars);
if (tries[_map.GetLocation(c)] != null)
nonNull = true;
chars.Enqueue(c);
}
}
if(nonNull)
return new ImmutableTrie(tries, false, _map);
return null;
}
