1. Linked List ADT used to store information in a list
Consists of a series of “linked” containers, called “nodes”, that hold the stored data
Each node contains:
Storage for one data element
A pointer to the next element in the list
The linked list maintains a pointer to the first element
The pointer stored in the last node is set to NULL

2. Linked List Node Node Node Node Data Data Data Data head Node* Node*
NULL

3. Advantages/Disadvantages
Can add additional items to the list without affecting existing items
Can insert items into arbitrary locations
Allows for maintaining a sorted list as elements are added
No wasted memory – only allocate what’s needed
Disadvantage
Access is not random
Locating an item requires a sequential search
Memory overhead (need to store pointers)
Storage is not localized

4. Source: www.slideshare.net

5. Iterators
A special class that is used to sequentially search a linked list
Needed to maintain “encapsulation”
Individual nodes (and pointers) should remain hidden from a user
Usually declared a “friend” of the linked list
Since it needs to keep track of the nodes in the list
A compromise to normal OOP practices

6. Iterator operation
Iterator maintains a pointer to a “current “ list node
Each sequential call to an update/next method moves the pointer to the next list node
Iterator starts at the head node
A method is provided to reset the pointer to the head so the iterator can be reused
A method is provided to access the stored data in the current node
Iterators shield the user from the details of
Node properties (and existence)
Pointer manipulation
Multiple iterators can be created for a given list

7. More complex Linked Lists
Linked lists can be made circular
“last” node points back to “first”
Doubly linked
Two pointers per node
Allows both forwards and backwards traversal