/// <summary>
/// Creates a clone of the current node as a sequence terminator node.
/// </summary>
/// <returns>The current node cloned as a sequence terminator.</returns>
/// <remarks>This method is primarily included for the case where a sequence is added to the trie which is a sub-sequence of an existing sequence (e.g. in the case of adding 'judge' when 'judgement' already exists). In such a case the last item in the new sequence being added needs to be changed from a TrieNode to a SequenceTerminatorTrieNode.</remarks>
public SequenceTerminatorTrieNode <T> CloneAsSequenceTerminator()
{
SequenceTerminatorTrieNode <T> clonedNode = new SequenceTerminatorTrieNode <T>(this.Item, this.ParentNode);
foreach (KeyValuePair <T, TrieNode <T> > currentChildNode in childNodes)
{
clonedNode.AddChildNode(currentChildNode.Key, currentChildNode.Value);
clonedNode.SetSubTreeSize(currentChildNode.Key, this.subtreeSizes[currentChildNode.Key]);
}
return(clonedNode);
}
/// <summary>
/// Creates a replica of the current node (i.e. a copy of the current node where the parent and child nodes hold the same item, but are not the same parent and child nodes as those of the current node).
/// </summary>
/// <returns>A replicated copy of the current node.</returns>
/// <remarks>This method is primarily included for unit tests where visibility of the internal trie structure is required, but without the risk of clients being able to modify the internal structure.</remarks>
public new SequenceTerminatorTrieNode <T> Replicate()
{
SequenceTerminatorTrieNode <T> replicaNode;
if (this.ParentNode != null)
{
replicaNode = new SequenceTerminatorTrieNode <T>(this.Item, new SequenceTerminatorTrieNode <T>(this.ParentNode.Item, null));
}
else
{
replicaNode = new SequenceTerminatorTrieNode <T>(this.Item, null);
}
foreach (T currentChildNodeItem in childNodes.Keys)
{
replicaNode.AddChildNode(currentChildNodeItem, new TrieNode <T>(currentChildNodeItem, replicaNode));
replicaNode.SetSubTreeSize(currentChildNodeItem, this.subtreeSizes[currentChildNodeItem]);
}
return(replicaNode);
}
/// <summary>
/// Adds the specified sequence of items to the trie.
/// </summary>
/// <param name="sequence">The sequence of items to add.</param>
/// <exception cref="System.ArgumentException">The specified sequence is empty.</exception>
/// <exception cref="System.ArgumentException">The specified sequence already exists in the trie.</exception>
public void Insert(IList <T> sequence)
{
ThrowExceptionIfSequenceCountIsZero(sequence);
TrieNode <T> currentNode = rootNode;
for (Int32 i = 0; i < sequence.Count; i++)
{
// Need special handling for the last item in the sequence
if (i == (sequence.Count - 1))
{
if (currentNode.ChildNodeExists(sequence[i]) == false)
{
// Create a new terminator node to hold the last item in the sequence
SequenceTerminatorTrieNode <T> newNode = new SequenceTerminatorTrieNode <T>(sequence[i], currentNode);
currentNode.AddChildNode(sequence[i], newNode);
}
else
{
TrieNode <T> existingNode = currentNode.GetChildNode(sequence[i]);
if (existingNode is SequenceTerminatorTrieNode <T> )
{
// If a node for the last item already exists and is a terminator node, throw an exception
Action <TrieNode <T>, TrieNode <T> > decrementCountsAction = (parentNode, childNode) =>
{
if (childNode != null)
{
parentNode.DecrementSubtreeSize(childNode.Item);
}
};
TraverseUpFromNode(existingNode.ParentNode, decrementCountsAction);
throw new ArgumentException($"The specified sequence {{ {ConvertSequenceToString(sequence)} }} already exists in the trie.", nameof(sequence));
}
else
{
// Convert the existing node for the last item into a terminator node
Int32 previousSubtreeSize = currentNode.GetSubtreeSize(sequence[i]);
SequenceTerminatorTrieNode <T> terminatorNode = existingNode.CloneAsSequenceTerminator();
currentNode.RemoveChildNode(sequence[i]);
currentNode.AddChildNode(sequence[i], terminatorNode);
currentNode.SetSubTreeSize(sequence[i], previousSubtreeSize + 1);
}
}
}
else
{
if (currentNode.ChildNodeExists(sequence[i]) == false)
{
TrieNode <T> newNode = new TrieNode <T>(sequence[i], currentNode);
currentNode.AddChildNode(sequence[i], newNode);
}
else
{
currentNode.IncrementSubtreeSize(sequence[i]);
}
}
currentNode = currentNode.GetChildNode(sequence[i]);
}
}
