//Utility functions for managing a Linked List
//Not what MS thinks is a "List". A real list, dammit.
//Add a new node as the pos'th item. 0 means add to front,
// -1 or a pos greater than the last item means add to end.
public static Node Add(Node head, string value, int pos)
{
//Create my new Node.
Node newNode = new Node();
newNode.Value = value;
//Am I adding to head?
if (head == null || pos == 0)
{
newNode.Next = head;
if (head != null) head.Previous = newNode;
newNode.Previous = null;
return newNode;
}
//Find the position I care about.
int position = 0;
Node current = head;
while (current.Next != null && (position < pos - 1 || pos == -1))
{
position++;
current = current.Next;
}
//At this point, I should be looking at either the last node,
//Or the node before position pos. Insert here.
newNode.Next = current.Next;
newNode.Previous = current;
current.Next = newNode;
return head;
}
static public Node Pop(Node stack, out string value)
{
if (stack == null)
{
value = "";
return null;
}
value = stack.Value;
Node newTop = stack.Next;
if (newTop != null) newTop.Previous = null;
return newTop;
}
public static Node InsertAlphabetical(Node head, string value)
{
//Insert at head?
if (head == null || string.Compare(head.Value, value) == 1)
{
return Add(head, value, 0);
}
//Otherwise, find insertion point
Node current = head;
int pos = 1;
while (current.Next != null && (string.Compare(current.Next.Value, value) < 1))
{
pos++;
current = current.Next;
}
return Add(head, value, pos);
}
static public string Peek(Node stack)
{
if (stack == null) throw new NullReferenceException("Stack is empty");
return stack.Value;
}
static public Node Push(Node stack,string value)
{
return List.Add(stack, value, 0);
}
static public string Peek(Node queue)
{
return Stack.Peek(queue);
}
static public Node Dequeue(Node queue, out string value)
{
return Stack.Pop(queue, out value);
}
static public Node Enqueue(Node queue, string value)
{
//Add to tail
return List.Add(queue, value, -1);
}
public static Node GetTail(Node head)
{
//Recursive, cause it's fun
if (head == null || head.Next == null) return head;
return GetTail(head.Next);
}
public static void PrintBackward(Node tail)
{
if (tail == null) { Console.WriteLine(); return; }
Console.Write(tail.Value + " ");
PrintBackward(tail.Previous);
}
//Print forward. Recursive
public static void PrintForward(Node head)
{
if (head == null) { Console.WriteLine(); return; }
Console.Write(head.Value + " ");
PrintForward(head.Next);
}
