/// <summary>
/// Performs the actual recursive insertion of the characters in the item into the Trie nodes
/// </summary>
/// <param name="node"></param>
/// <param name="item"></param>
/// <param name="index"></param>
protected void AddRecursive(TrieNode node, String item, int index)
{
// If we are at and end of word - mark the node as ending a word
if (item.Length == index)
{
node.EndsWord = true;
return;
}
char firstChar = item[index];
TrieNode childNode = node.AddOrGetNode(firstChar);
if (childNode != null)
{
AddRecursive(childNode, item, index + 1);
}
}
/// <summary>
/// Performs the actual recursive lookup of the characters in the item
/// </summary>
/// <param name="node">node to search for matches</param>
/// <param name="item">string to be looked-up</param>
/// <returns>returns </returns>
protected TrieNode FindPrefixRecursive(TrieNode node, string item)
{
if (String.IsNullOrEmpty(item))
{
return node;
}
char firstChar = item[0];
TrieNode childNode = node.GetChildNode(firstChar);
// If there is no corresponding node, then we didn't find our item - return null.
if (childNode == null)
{
return null;
}
else
{
// we did find our matching node - go to it and continue matching the rest of the string
return FindPrefixRecursive(childNode, item.Substring(1));
}
}
/// <summary>
/// Adds the requested character to the Node subtree children
/// If there is already a child representing the character - return it
/// </summary>
/// <param name="c"></param>
/// <returns></returns>
public TrieNode AddOrGetNode(char c)
{
TrieNode newNode;
if (_children == null)
_children = new Dictionary<char, TrieNode>();
if (!_children.TryGetValue(c, out newNode))
{
// children do not contain c, add a TrieNode
newNode = new TrieNode(c);
_children.Add(c, newNode);
}
return newNode;
}
/// <summary>
/// Trie Consructor
/// </summary>
public Trie()
{
_rootNode = new TrieNode(' ');
}
/// <summary>
/// Performs the actual lookup for the all words contained in the subtree.
/// </summary>
/// <param name="node">root node of a subtree to look for contained words</param>
/// <param name="wordBuilder">a StringBuilder to perform fast character appending</param>
/// <param name="completionSetCount">maximum number of words to return</param>
/// <param name="completions">A list to contain all the words that are found</param>
protected void GetCompletionsRecursive(TrieNode node, StringBuilder wordBuilder, int completionSetCount, List<String> completions)
{
if ((node == null) || (completions.Count >= completionSetCount))
{
// no match or we have enough matches to fulfil request - rollback builder and return
wordBuilder.Length -= 1;
return;
}
if (node.EndsWord)
{
// end reached, append the built word into completions list.
completions.Add(wordBuilder.ToString());
}
IDictionary<char, TrieNode> childNodes = node.Children;
if (childNodes != null)
{
foreach (KeyValuePair<char, TrieNode> pair in childNodes)
{
char childChar = pair.Value.Character;
wordBuilder.Append(childChar);
GetCompletionsRecursive(pair.Value, wordBuilder, completionSetCount, completions);
}
}
wordBuilder.Length -= 1;
}
