public DoublyLLNode InsertAtHead(int val)
{
if (head != null)
{
var nodeToAdd = new DoublyLLNode(val);
nodeToAdd.Next = head;
head.Prev = nodeToAdd;
head = nodeToAdd;
return(head);
}
head = new DoublyLLNode(val);
return(head);
}
public void RemoveNode(DoublyLLNode node)
{
if (head != null && head != node)
{
var prev = node.Prev;
var next = node.Next;
if (prev != null)
{
prev.Next = next;
}
if (next != null)
{
next.Prev = prev;
}
node.Prev = null;
node.Next = null;
return;
}
head = null;
return;
}
public void UpgradeToHead(DoublyLLNode node)
{
if (head != null && head != node)
{
var prev = node.Prev;
var next = node.Next;
if (prev != null)
{
prev.Next = next;
}
if (next != null)
{
next.Prev = prev;
}
node.Prev = head.Prev;
node.Next = head;
head.Prev = node;
head = node;
return;
}
head = node;
return;
}
public DoublyLLNode(int val, DoublyLLNode prev = null, DoublyLLNode next = null)
{
Data = val;
Prev = prev;
Next = next;
}
