public static DoublyLinkedListNode <int> InsertAtTail(DoublyLinkedListNode <int> head, int data)
{
DoublyLinkedListNode <int> newNode = new DoublyLinkedListNode <int>(data);
if (head == null)
{
head = newNode;
return(head);
}
DoublyLinkedListNode <int> lastNode = head;
while (lastNode.Next != null)
{
lastNode = lastNode.Next;
}
newNode.Prev = lastNode;
lastNode.Next = newNode;
return(head);
}
public static DoublyLinkedListNode <int> Reverse(DoublyLinkedListNode <int> head)
{
if (head == null)
{
return(head);
}
DoublyLinkedListNode <int> current = head;
DoublyLinkedListNode <int> newHead = head;
while (current != null)
{
DoublyLinkedListNode <int> prev = current.Prev;
current.Prev = current.Next;
current.Next = prev;
newHead = current;
current = current.Prev; // Item in the next in iteration has been the prev of current.
}
return(newHead);
}
public static DoublyLinkedListNode <int> InsertSorted(DoublyLinkedListNode <int> head, int data)
{
DoublyLinkedListNode <int> newNode = new DoublyLinkedListNode <int>(data);
if (head == null)
{
return(newNode);
}
if (data <= head.Data)
{
newNode.Next = head;
head.Prev = newNode;
return(newNode);
}
DoublyLinkedListNode <int> currentNode = head;
while (currentNode.Next != null && data > currentNode.Next.Data)
{
currentNode = currentNode.Next;
}
DoublyLinkedListNode <int> nextOfCurrent = currentNode.Next;
newNode.Next = nextOfCurrent;
if (nextOfCurrent != null)
{
nextOfCurrent.Prev = newNode;
}
newNode.Prev = currentNode;
currentNode.Next = newNode;
return(head);
}
