/// <summary>
/// delete a word from the tree means delete the last leaf that makes up the stored word
/// </summary>
/// <param name="label"></param>
/// <param name="curNode"></param>
public void DeleteRec(string wordPart, Node curNode)
{
var matches = MatchingConsecutiveCharacters(wordPart, curNode);
if ((matches == 0) || (curNode == _root) ||
((matches > 0) && (matches < wordPart.Length) && (matches >= curNode.Label.Length)))
{
var newLabel = wordPart.Substring(matches, wordPart.Length - matches);
foreach (var child in curNode.SubNodes)
if (child.Label.StartsWith(newLabel[0].ToString()))
{
if (newLabel == child.Label)
{
if (child.SubNodes.Count == 0)
{
curNode.SubNodes.Remove(child);
return;
}
}
DeleteRec(newLabel, child);
}
}
}
public TrieNode(Node n)
{
this.n = n;
indx = 0;
if (n.Label.Length == 0)
{
c = '$';
}
else
c = n.Label[indx];
}
public void CreateTree()
{
tree = Node<string>.Root();
}
public TrieNode(Node n, int indx)
{
this.n = n;
this.indx = indx + 1;
c = n.Label[this.indx];
}
/// <summary>
/// given a string and a node the number of characters that the string and the node's label have
/// in common starting from the first character in each is returned
/// </summary>
/// <param name="word">a string that is to be compared with the node's label</param>
/// <param name="curNode">a node</param>
/// <returns></returns>
private int MatchingConsecutiveCharacters(string word, Node curNode)
{
int matches = 0;
int minLength = 0;
//see which string is smaller and save it's lenght
//when cycling throught the two strings we won't go any further than that
if (curNode.Label.Length >= word.Length)
minLength = word.Length;
else if (curNode.Label.Length < word.Length)
minLength = curNode.Label.Length;
if(minLength > 0)
//go throught the two streams
for (int i = 0; i < minLength; i++)
{
//if two characters at the same position have the same value we have one more match
if(word[i] == curNode.Label[i])
matches++;
else
//if at any position the two strings have different characters break the cycle
break;
}
//and return the current number of matches
return matches;
}
/// <summary>
/// look for a word in the tree begining at the current node
/// </summary>
/// <param name="wordPart"></param>
/// <param name="curNode"></param>
/// <returns></returns>
private bool LookupRec(string wordPart, Node curNode)
{
var matches = MatchingConsecutiveCharacters(wordPart, curNode);
if ((matches == 0) || (curNode == _root) ||
((matches > 0) && (matches < wordPart.Length) && (matches >= curNode.Label.Length)))
{
var newLabel = wordPart.Substring(matches, wordPart.Length - matches);
foreach (var child in curNode.SubNodes)
if (child.Label.StartsWith(newLabel[0].ToString()))
return LookupRec(newLabel, child);
return false;
}
else if (matches == curNode.Label.Length)
{
return true;
}
else return false;
}
/// <summary>
/// construct a new tree with it's root
/// </summary>
public Tree()
{
_root = new Node("");
}
/// <summary>
/// recursively traverse the tree
/// carry the word you want inserted until a proper place for it is found and it can be inserted there
/// if a node already stores a substring of the word(substrnig with the same first letter as the word itself)
/// then that substring must be removed from the word and it's children checked out next
/// hence the name wordPart - part of a word
/// </summary>
/// <param name="wordPart">the part of the word that is to be inserted that is not already included in any of the tree's nodes</param>
/// <param name="curNode">the node currently traversed</param>
private void InsertRec(string wordPart, Node curNode)
{
//get the number of characters that the word part that is to be inserted and the current node's label have
//in common starting from the first position of both strings
//matching characters in the two strings = have the same value at the same position in both strings
var matches = MatchingConsecutiveCharacters(wordPart, curNode);
//if we are at the root node
//OR
//the number of characters from the two strings that match is
//bigger than 0
//smaller than the the part of the word that is to be inserted
//bigger than the the label of the current node
if ((matches == 0) || (curNode == _root) ||
((matches > 0) && (matches < wordPart.Length) && (matches >= curNode.Label.Length)))
{
//remove the current node's label from the word part
bool inserted = false;
var newWordPart = wordPart.Substring(matches, wordPart.Length - matches);
//search the node's subnodes and if the subnode label's first character matches
//the word part's first character then insert the word part after this node(call the
//current method recursively)
foreach(var child in curNode.SubNodes)
if (child.Label.StartsWith(newWordPart[0].ToString()))
{
inserted = true;
InsertRec(newWordPart, child);
}
if (inserted == false)
{
curNode.SubNodes.Add(new Node(newWordPart));
}
}
else if(matches < wordPart.Length)
{
//in this case we have to nodes that we must add to the tree
//one is the node that has a label extracted from the current node's label without the string of
//matching characters(common characters)
//the other is the node that has it's label extracted from the current word part minus the string
//of matching characters
string commonRoot = wordPart.Substring(0, matches);
string branchPreviousLabel = curNode.Label.Substring(matches, curNode.Label.Length - matches);
string branchNewLabel = wordPart.Substring(matches, wordPart.Length - matches);
curNode.Label = commonRoot;
var newNodePreviousLabel = new Node(branchPreviousLabel);
newNodePreviousLabel.SubNodes.AddRange(curNode.SubNodes);
curNode.SubNodes.Clear();
curNode.SubNodes.Add(newNodePreviousLabel);
var newNodeNewLabel = new Node(branchNewLabel);
curNode.SubNodes.Add(newNodeNewLabel);
}
else if (matches == curNode.Label.Length)
{
//in this case we don't do anything because the word is already added
}
else if (matches > curNode.Label.Length)
{
//add the current word part minus the common characters after the current node
string newNodeLabel = curNode.Label.Substring(curNode.Label.Length, wordPart.Length);
var newNode = new Node(newNodeLabel);
curNode.SubNodes.Add(newNode);
}
}
private string FindSuccessorRec(string wordPart, Node curNode,string carry)
{
var matches = MatchingConsecutiveCharacters(wordPart, curNode);
if ((matches == 0) || (curNode == _root) ||
((matches > 0) && (matches < wordPart.Length) ))
{
var newLabel = wordPart.Substring(matches, wordPart.Length - matches);
foreach (var child in curNode.SubNodes)
if (child.Label.StartsWith(newLabel[0].ToString()))
return FindSuccessorRec(newLabel, child, carry + curNode.Label);
return curNode.Label;
}
else if (matches < curNode.Label.Length)
{
return carry + curNode.Label;
}
else if (matches == curNode.Label.Length)
{
carry = carry + curNode.Label;
int min = int.MaxValue;
int index = -1;
for (int i = 0; i < curNode.SubNodes.Count;i++ )
if (curNode.SubNodes[i].Label.Length < min)
{
min = curNode.SubNodes[i].Label.Length;
index = i;
}
if (index > -1)
return carry + curNode.SubNodes[index].Label;
else
return carry;
}
else return string.Empty;
}
/// <summary>
/// </summary>
/// <param name="wordPart"></param>
/// <param name="curNode"></param>
/// <returns></returns>
private string FindPredecessorRec(string wordPart, Node curNode,string carry)
{
var matches = MatchingConsecutiveCharacters(wordPart, curNode);
if ((matches == 0) || (curNode == _root) ||
((matches > 0) && (matches < wordPart.Length) && (matches >= curNode.Label.Length)))
{
var newLabel = wordPart.Substring(matches, wordPart.Length - matches);
foreach (var child in curNode.SubNodes)
if (child.Label.StartsWith(newLabel[0].ToString()))
return FindPredecessorRec(newLabel, child, carry + curNode.Label);
return carry + curNode.Label;
}
else if (matches == curNode.Label.Length)
{
return carry + curNode.Label;
}
else return string.Empty;
}
