/* pre: Have object to be added to calling singly linked list object, and a link in the singly linked list AFTER
* which the newItem's node must be added.
* post: newItem is the element of the added node of the singly linked list. All other existing nodes of the
* singly linked list retain their ordering relevant to the position of the newly added node.
* The counter is modified to reflect the addition of a new node to the singly linked list. */
public void addAfter(Object newItem, Node link)
{
if (link == null)
{
this.addLast(newItem);
return;
}
Node newNode = new Node(newItem);
Node cur = head;
Node prev = head;
while (prev != link)
{
prev = cur;
cur = cur.next();
}
if (prev == cur)
{
newNode.setNext(cur.next());
cur.setNext(newNode);
counter++;
return;
}
prev.setNext(newNode);
newNode.setNext(cur);
counter++;
}
/* pre: Have object to be added to calling singly linked list object, and a link in the singly linked list BEFORE
* which the newItem's node must be added.
* post: newItem is the element of the added node of the singly linked list. All other existing nodes of the
* singly linked list retain their ordering relevant to the position of the newly added node.
* The counter is modified to reflect the addition of a new node to the singly linked list. */
public void addBefore(Object newItem, Node link)
{
if (link == null) // list either empty or must be added at end of list
{
this.addLast(newItem);
return;
}
Node newNode = new Node(newItem);
Node cur = head;
if (cur == link) // must be added as first node
{
this.addFirst(newItem);
return;
}
while (cur.next() != link)
cur = cur.next();
cur.setNext(newNode);
newNode.setNext(link);
counter++;
}
/* pre: Have object to be added to calling singly linked list object, which may be empty.
* post: newItem is the element of the FIRST node of the singly linked list. All other existing nodes of the
* singly linked list retain their ordering AFTER the new first node.
* The counter is modified to reflect the addition of a new node to the singly linked list. */
public void addFirst(Object newItem)
{
Node newNode = new Node(newItem);
newNode.setNext(head);
head = newNode;
counter++;
}
protected Node head; // points to first node in the list
#endregion Fields
#region Constructors
public SinglyLinkedList()
{
counter = 0;
head = null;
}
/* pre: Have at least one node in calling singly linked list object.
* post: Return the node removed, which is the first node in the list.
* The counter is modified to reflect the removal of the first node from the singly linked list. */
public Node removeFirst()
{
Node cur = head;
head = cur.next();
cur.setNext(null);
counter--;
return cur;
}
/* pre: Have at least one node in calling singly linked list object.
* post: Return the node removed, which is the last node in the list.
* The counter is modified to reflect the removel of the last node from the singly linked list. */
public Node removeLast()
{
Node cur = head;
Node prev = head;
while (cur.next() != null)
{
prev = cur;
cur = cur.next();
}
if (prev == cur)
head = null;
else
prev.setNext(null);
counter--;
return cur;
}
/* pre: Have object to be added to calling singly linked list object, which may be empty.
* post: newItem is the element of the LAST node of the singly linked list. All other existing nodes of the
* singly linked list retain their ordering BEFORE the new last node.
* The counter is modified to reflect the addition of a new node to the singly linked list. */
public void addLast(Object newItem)
{
if (this.Count() == 0)
{
this.addFirst(newItem);
return;
}
Node newNode = new Node(newItem);
Node cur = head;
Node prev = head;
while (cur != null)
{
prev = cur;
cur = cur.next();
}
prev.setNext(newNode);
counter++;
}
public void setNext(Node theLink)
{
Link = theLink;
}
public Node()
{
Element = null;
Link = null;
}
public Node(Object theElement)
{
Element = theElement;
Link = null;
}
public Node(Object theElement, Node theLink)
{
Element = theElement;
Link = theLink;
}