public void InsertAt(int position, T value)
{
this.ThrowIfInvalidPosition(position);
if (position == 0)
{
if (this.Head == null)
{
DoubleNode <T> node = new DoubleNode <T>(value, null, null);
node.Next = node;
node.Previous = node;
this.Head = node;
this.Tail = node;
}
else
{
DoubleNode <T> node = new DoubleNode <T>(value, this.Tail, this.Head);
this.Head.Previous = node;
this.Head = node;
}
this.Tail !.Next = this.Head;
}
else if (position >= this.Count - 1)
{
DoubleNode <T> node = new DoubleNode <T>(value, this.Tail, this.Head);
this.Head !.Previous = node;
this.Tail !.Next = node;
this.Tail = node;
}
else
{
DoubleNode <T> parent = this.Head !;
for (int i = 1; i < position; i++)
{
parent = parent.Next !;
}
DoubleNode <T> node = new DoubleNode <T>(value, parent, parent.Next);
parent.Next !.Previous = node;
parent.Next = node;
}
this.Count++;
}
public void DeleteAt(int position)
{
this.ThrowIfEmpty();
this.ThrowIfInvalidPosition(position);
if (position == 0)
{
DoubleNode <T> head = this.Head !;
if (head !.Next == null)
{
this.Head !.Next = null;
this.Head = null;
this.Tail !.Previous = null;
this.Tail = null;
}
else
{
this.Head = head.Next;
this.Head.Previous = null;
head.Next = null;
}
}
