public override void AddFirst(T item)
{
//create node.
var node = new DoublyNode <T>(item);
// Make next of new node as head and previous as null.
node.Next = head;
node.Prev = null;
//change prev of head node to new null.
if (head != null)
{
head.Prev = node;
}
//move the head to point to the new node
head = node;
count++;
}
public override bool AddAfter(T nodeData, T item)
{
var current = head;
while (current != null)
{
if (IsEquals(current.Data, nodeData))
{
var node = new DoublyNode <T>(item);
node.Prev = current;
node.Next = current.Next;
current.Next = node;
count++;
return(true);
}
current = current.Next;
}
return(false);
}
public override bool AddBefore(T nodeData, T item)
{
var current = head;
var node = new DoublyNode <T>(item);
if (current != null && IsEquals(current.Data, nodeData))
{
node.Next = head;
head.Prev = node;
if (count == 1)
{
node.Prev = head;
head.Next = node;
}
else
{
node.Prev = head.Prev;
head.Prev.Next = node;
}
head = node;
count++;
return(true);
}
else
{
while (current != null && current.Next != head)
{
if (IsEquals(current.Next.Data, nodeData))
{
node.Next = current.Next;
node.Prev = current;
current.Next = node;
current.Next.Prev = node;
count++;
return(true);
}
current = current.Next;
}
}
return(false);
}
public virtual void Clear()
{
head = null;
count = 0;
}
protected T GetData(DoublyNode <T> node) => node != null ? node.Data : default(T);