I am doing the following task (in c#): We have a group of letters and an english dictionary. Find all possible combinations of words that are created from the letters provided. To do that, I use trie data structure - I search for words and all possible additional words from remaining letters(recursive operation). However, the operation is very time/space consuming. Any idea how to handle it more efficiently ?
EDIT This is example code I prepared:
class Trie
{
private Node root = new Node(null);
public void AddWord(string word)
{
root.Add(word, 0);
}
public void GetCandidates(string input)
{
var results = new List<Result>()
{
new Result() {Rest = input}
};
Get(results);
}
private void Get(List<Result> results)
{
foreach (var result in results.Where(r => !string.IsNullOrEmpty(r.Rest)).ToList())
{
var pattern = result.Rest.Replace(" ", string.Empty);
var allWords = new List<Result>();
root.GetWord(string.Empty, allWords, pattern);
result.OhterWords = allWords;
Get(allWords);
}
}
}
class Node
{
protected Dictionary<char,Node> children = new Dictionary<char, Node>();
public bool End { get; private set; }
public char? Key { get; private set; }
public Node(char? key)
{
Key = key;
}
public void Add(string word, int index)
{
var letter = word[index];
if (!children.ContainsKey(letter))
{
children.Add(letter, new Node(letter));
}
var nextIndex = index + 1;
if (nextIndex < word.Length)
{
children[letter].Add(word, nextIndex);
}
else
{
children[letter].End = true;
}
}
public virtual void GetWord(string current, List<Result> allWords, string availableLetters)
{
var newCurrent = string.Concat(current, Key);
if (End)
{
var result = new Result()
{
Rest = availableLetters,
Word = newCurrent,
};
if (!allWords.Contains(result))
{
allWords.Add(result);
}
}
foreach (var letter in availableLetters)
{
if (children.ContainsKey(letter))
{
var index = availableLetters.IndexOf(letter);
var tempAvailableString = availableLetters.Remove(index, 1);
children[letter].GetWord(newCurrent, allWords, tempAvailableString);
}
}
}
}
class Result
{
public List<Result> OhterWords { get; set; }
public string Word { get; set; }
public string Rest { get; set; }
public override bool Equals(object obj)
{
var r = obj as Result;
if (r == null)
{
return false;
}
return r.Word == Word && r.Rest == Rest;
}
}
