IEnumerator <T> IEnumerable <T> .GetEnumerator()
{
DoubleLinkNode <T> node = FirstNode;
while (node != null)
{
yield return(node.Value);
node = node.Next;
}
}
void ICollection <T> .CopyTo(T[] array, int arrayIndex)
{
DoubleLinkNode <T> node = FirstNode;
while (node.Next != null)
{
array[arrayIndex] = node.Value;
arrayIndex++;
node = node.Next;
}
}
bool ICollection <T> .Contains(T item)
{
DoubleLinkNode <T> node = FirstNode;
while (node.Next != null)
{
if (node.Value.Equals(item))
{
return(true);
}
node = node.Next;
}
return(false);
}
bool ICollection <T> .Remove(T item)
{
if (Count == 0)
{
return(false);
}
else
{
DoubleLinkNode <T> previousNode = null;
DoubleLinkNode <T> currenNode = FirstNode;
while (currenNode != null)
{
if (currenNode.Value.Equals(item))
{
// Match found
if (previousNode != null)
{
// PreviousNode is set, we are past first node
// Change pointers (disconnect previous -> current)
previousNode.Next = currenNode.Next;
// If current node was last node, previous becomes new Last
if (currenNode.Next == null)
{
LastNode = previousNode;
}
Count--;
}
else
{
// Previous node never set, remove first node
RemoveFirst();
}
return(true);
}
// Move pointers
previousNode = currenNode;
currenNode = currenNode.Next;
}
return(false);
}
}
/// <summary>
/// Add node to end of the list.
/// </summary>
/// <param name="node"></param>
private void AddLast(DoubleLinkNode <T> node)
{
if (FirstNode == null && LastNode == null)
{
// New linked list. Incoming `node` is First and Last
FirstNode = node;
LastNode = FirstNode;
}
else
{
// Point last node to incoming `node`. Set `node` as Last.
LastNode.Next = node;
node.Previous = LastNode;
LastNode = node;
}
Count++;
}
public void RemoveLast()
{
if (Count > 0)
{
if (Count == 1)
{
FirstNode = LastNode = null;
}
else
{
// Get second to last node
DoubleLinkNode <T> node = LastNode.Previous;
node.Next = null;
LastNode = node;
}
Count--;
}
}
/// <summary>
/// Add node to beginning of list.
/// </summary>
/// <param name="node"></param>
private void AddFirst(DoubleLinkNode <T> node)
{
// Copy first node
DoubleLinkNode <T> previousFirst = FirstNode;
// Make incoming `node` first
FirstNode = node;
// New first node will now point to previous first node
FirstNode.Next = previousFirst;
// If this is a new linked list,
// First and Last are the same
if (LastNode == null)
{
LastNode = FirstNode;
}
else
{
previousFirst.Previous = FirstNode;
}
Count++;
}
