Review of operations on a linked list

Operations on a linked list:

Insert a new item into the linked list (at any position):
Remove an item from the linked list (at any position)
Retrieve an item from the linked list (at any position)

The principle of each type of algorithm is always the same

Therefore:

Do not memorize
Understand what needs to be done

Understand the list manipulation operations, such as:

current = current.next; current.next = new Node( ... );

The insert algorithm

Inserting a new node after a node X:

(1) Find the node X with the list traversal algorithm: Node<T> current = first; while ( current != null && current != "node X" ) { current = current.next; } (2) Link the new node after current if node X was found: if ( current == null ) handle "not found"; current.next = new Node( ...., current.next ); Notice the general case updates current.next

Edge case: when insertion requires updating first
Inserting into an empty list
The new node becomes the 1st node in the list

The retrieval algorithm

Retrieve the item stored in a node X:

(1) Find the node X with the list traversal algorithm: Node<T> current = first; while ( current != null && current != "node X" ) { current = current.next; } (2) Return the item if node X was found: if ( current == null ) handle "not found"; return current.item; Notice the general case updates current.next

Edge case: none

The delete algorithm

Deleting a node X from a linked list:

(1) Find the node X while tracking its predecessor with the list traversal algorithm: Node<T> previous = first; Node<T> current = first; while ( current != null && current != "node X" ) { previous = current; current = current.next; } (2) Unlink the node X from previous if node X was found: if ( current == null ) handle "not found"; previous.next = current.next; Notice the general case updates previous.next

Edge case: (1) empty list and (2) when deletion requires updating first

(2a) Delete the last remaining node from a list (must set first = null)
(2b) Delete the first node from a list (must set first = first.next)