1. LINKED LISTS
A linked list is a collection of data in which each element contains the location of the next element—that is, each element contains two parts: data and link. The name of the list is the same as the name of this pointer variable. Figure 11.9 shows a linked list called scores that contains four elements. We define an empty linked list to be only a null pointer: Figure 11.9 also shows an example of an empty linked list.

2. Figure Linked lists

3. Abstract Data Types (ADT)
Definition :
Is a set of operation
Mathematical abstraction
No implementation detail
Example :
Lists, sets, graphs, stacks are examples of ADT along with their operations

4. THE LIST ADT Ordered sequence of data items called elements
A1, A2, A3, …,AN is a list of size N
size of an empty list is 0
Ai+1 succeeds Ai
Ai-1 preceeds Ai
position of Ai is i
first element is A1 called “head”
last element is AN called “tail”
Operations ?

5. Outline Linked list nodes Linked list operations
Insertion
Append
Deletion
Linked list representation & implementation
Other types of linked lists
Sorted
Doubly-linked
Circular
1st March 2007

6. Array vs Linked List
node
node
Array
node
Linked List

7. Linked List Implementation of Lists
Series of nodes
not adjacent in memory
contain the element and a pointer to a node containing its succesor
Avoids the linear cost of insertion and deletion !

8. Linked List Implementation of Lists
Series of nodes
not adjacent in memory
contain the element and a pointer to a node containing its succesor
Avoids the linear cost of insertion and deletion !

9. Linked List Implementation of Lists
Linked List Array
PrintList O(N) (traverse the list) O(N)
Find
FindKth (L,i) O(i) O(1)
Delete O(1) O(N)
Insert

10. Doubly Linked List Traversing list backwards
not easy with regular lists
Insertion and deletion more pointer fixing
Deletion is easier
Previous node is easy to find

11. Circulary Linked List
Last node points the first

12. Cursor Implementation of Linked List
If L = 5, then L represents list (A, B, E)
If M = 3, then M represents list (C, D, F)

13. Linked List: Insertiona b c d
current
Insert X immediately after current position a b c d x
current
1st March 2007

14. Inserting a Node
When inserting a node in the middle of a linked list, we must first find the spot to insert it
Let current refer to the node before the spot where the new node will be inserted

15. Implementing Insertion: Step By Step
Insertion immediately after current position
// create a new node
tmp = new ListNode<DataType>();
// place x in the element field
tmp.data = x; a b x
current
tmp
1st March 2007

16. Implementing Insertion: Step By Step
Insertion immediately after current position
// create a new node
tmp = new ListNode<DataType>();
// place x in the element field
tmp.data = x;
// x’s next node is b
tmp.next = current.next; a b x
current
tmp
1st March 2007

17. Implementing Insertion: Step By Step
Insertion immediately after current position
// create a new node
tmp = new ListNode<DataType>();
// place x in the element field
tmp.data = x;
// x’s next node is b
tmp.next = current.next;
// a’s next node is x
current.next = tmp; a b x
current
tmp
1st March 2007

18. Implementing Insertion: Shortest Version
An even shorter version:
// create a new node
current.next = new ListNode<DataType>(x,current.next); a b x
current
1st March 2007

19. Inserting a Node
A method called insert could be defined to add a node anywhere in the list, to keep it sorted, for example
Inserting at the front of a linked list is a special case

20. Implementing Basic Deletion
Delete an item immediately after current position
Basic deletion is a bypass in the linked list. a x b
current a b
current
1st March 2007

21. Other Linked Lists
Doubly-linked lists: Each list node stores both the previous and next nodes in the list. Useful for traversing linked lists in both directions.
Circular-linked lists: Last node's next references the first node. Works with or without headers. A
head
tail
prev
next
prev A B C
next
first
1st March 2007