/// <summary>
/// Marks this data as the new reference node after insertion.
/// Like insert first assuming that current reference node as head.
/// Time complexity: O(1).
/// </summary>
public CircularLinkedListNode <T> Insert(T data)
{
var newNode = new CircularLinkedListNode <T>(data);
//if no item exist
if (ReferenceNode == null)
{
//attach the item after reference node
newNode.Next = newNode;
newNode.Previous = newNode;
}
else
{
//attach the item after reference node
newNode.Previous = ReferenceNode;
newNode.Next = ReferenceNode.Next;
ReferenceNode.Next.Previous = newNode;
ReferenceNode.Next = newNode;
}
ReferenceNode = newNode;
return(newNode);
}
/// <summary>
/// Time complexity: O(1).
/// </summary>
public void Clear()
{
if (ReferenceNode == null)
{
throw new Exception("Empty list");
}
ReferenceNode = null;
}
//O(1) always
public void DeleteAll()
{
if (ReferenceNode == null)
{
throw new Exception("Empty list");
}
ReferenceNode = null;
}
//search and delete
//cost O(n) in worst case O(nlog(n) average?
public void Delete(T data)
{
if (ReferenceNode == null)
{
throw new Exception("Empty list");
}
//only one element on list
if (ReferenceNode.Next == ReferenceNode)
{
if (ReferenceNode.Data.Equals(data))
{
ReferenceNode = null;
return;
}
throw new Exception("Not found");
}
//atleast two elements from here
var current = ReferenceNode;
var found = false;
while (true)
{
if (current.Data.Equals(data))
{
current.Prev.Next = current.Next;
current.Next.Prev = current.Prev;
//match is a reference node
if (current == ReferenceNode)
{
ReferenceNode = current.Next;
}
found = true;
break;
}
//terminate loop if we are about to cycle
if (current.Next == ReferenceNode)
{
break;
}
///move to next item
current = current.Next;
}
if (found == false)
{
throw new Exception("Not found");
}
}
public bool MoveNext()
{
if (referenceNode == null)
{
return(false);
}
if (currentNode == null)
{
currentNode = referenceNode;
return(true);
}
if (currentNode.Next != null && currentNode.Next != referenceNode)
{
currentNode = currentNode.Next;
return(true);
}
return(false);
}
//O(1) delete this item
public void Delete(CircularLinkedListNode <T> current)
{
if (ReferenceNode.Next == ReferenceNode)
{
if (ReferenceNode == current)
{
ReferenceNode = null;
return;
}
throw new Exception("Not found");
}
current.Prev.Next = current.Next;
current.Next.Prev = current.Prev;
//match is a reference node
if (current == ReferenceNode)
{
ReferenceNode = current.Next;
}
}
public void Dispose()
{
referenceNode = null;
currentNode = null;
}
public void Reset()
{
currentNode = referenceNode;
}
internal CircularLinkedListEnumerator(ref CircularLinkedListNode <T> referenceNode)
{
this.referenceNode = referenceNode;
}