// To make things fast, I should break down all the words in the dictionary in sequence of letters, as an indication there is a word I want, for example:
// each entry should tellme whether there is a word that ends at that entry and whether there are subwords
// if the dictionary contains the word: bread, then I need the following:
// entry | IsWord | HasChildren
// b n y
// br n y
// bre n y
// brea n y
// bread y y
// if the dictionary contains bread and bred then:
// entry | IsWord | HasChildren
// b n y
// br n y
// bre n y
// brea n y
// bred y y
// bread y y
public static DictionaryLookupInfo BuildLookupInfo(Dictionary dictionary)
{
DictionaryLookupInfo result = new DictionaryLookupInfo();
foreach (string w in dictionary.Words)
{
// only words MinWordLength char or more.
if (w.Length < dictionary.MinWordLength)
{
continue;
}
StringBuilder sb = new StringBuilder();
for (int i = 0; i < w.Length; i++)
{
sb.Append(w[i]);
WordLookupInfoData id = new WordLookupInfoData();
string key = sb.ToString();
if (result.LookupInfo.ContainsKey(key))
{
id = result.LookupInfo[key];
}
id.IsWord |= (i == (w.Length - 1));
id.HasChildren |= (i < (w.Length - 1));
result.LookupInfo[key] = id;
}
}
return(result);
}
// main function: depth first search in the board, using the lookup map and a temp string
private static List <string> FindWordsFromCell(GameBoard board, DictionaryLookupInfo lookup, int i, int j, bool[,] boardVisitedInfo, StringBuilder tempword)
{
List <string> result = new List <string>();
// we need to look if the char concatenated with the optional string in the recursive call has an entry.
char cellChar = board.Board[i, j];
tempword.Append(cellChar);
string tempwordstring = tempword.ToString();
// if the word is in the lookup map
if (lookup.LookupInfo.ContainsKey(tempwordstring))
{
WordLookupInfoData map_entry = lookup.LookupInfo[tempwordstring];
// if so, if it is a word, add it to the colletion.
if (map_entry.IsWord)
{
// we have found a word!
result.Add(tempwordstring);
}
// if it has possible children
if (map_entry.HasChildren)
{
// mark the cell as used.
boardVisitedInfo[i, j] = true;
// for all the non marked children
foreach (var neigh in board.Neighbors[i, j])
{
if (!boardVisitedInfo[neigh.Item1, neigh.Item2])
{
// recursion call
result.AddRange(FindWordsFromCell(board, lookup, neigh.Item1, neigh.Item2, boardVisitedInfo, tempword));
}
}
// unmark the current cell
boardVisitedInfo[i, j] = false;
}
}
// backtrack the temp string
tempword.Remove(tempword.Length - 1, 1);
return(result);
}
// Note: it will return words in lower case, as input is normalized to be lower case
static public HashSet <string> FindWords(GameBoard board, Dictionary dictionary)
{
HashSet <string> result = new HashSet <string>();
// fill up the map with the info in the dictionary
DictionaryLookupInfo lookup = DictionaryLookupInfo.BuildLookupInfo(dictionary);
// for each cell in the board
for (int i = 0; i < board.Size; i++)
{
for (int j = 0; j < board.Size; j++)
{
bool[,] boardVisitedInfo = InitVisitedInfo(board.Size);
result.UnionWith(FindWordsFromCell(board, lookup, i, j, boardVisitedInfo, new StringBuilder()));
}
}
return(result);
}
