1. C++ Programming:. Program Design Including
C++ Programming: Program Design Including Data Structures, Fourth Edition
Chapter 17: Linked Lists

2. Objectives In this chapter, you will: Learn about linked lists
Become aware of the basic properties of linked lists
Explore the insertion and deletion operations on linked lists
Discover how to build and manipulate a linked list
Learn how to construct a doubly linked list
C++ Programming: Program Design Including Data Structures, Fourth Edition

3. Introduction
Data can be organized and processed sequentially using an array, called a sequential list
Problems with an array
Array size is fixed
Unsorted array: searching for an item is slow
Sorted array: insertion and deletion is slow
C++ Programming: Program Design Including Data Structures, Fourth Edition

4. Linked Lists
Linked list: a list of items (nodes), in which the order of the nodes is determined by the address, called the link, stored in each node
Link field in last node
is NULL
C++ Programming: Program Design Including Data Structures, Fourth Edition

5. Linked Lists (continued)
Example:
Suppose that the first node is at memory location 1200, and the second node is at memory location 1575
C++ Programming: Program Design Including Data Structures, Fourth Edition

6. Linked Lists (continued)
Because each node of a linked list has two components, we need to declare each node as a class or struct
Data type of a node depends on the specific application
The link component of each node is a pointer
C++ Programming: Program Design Including Data Structures, Fourth Edition

7. Linked Lists: Some Properties
C++ Programming: Program Design Including Data Structures, Fourth Edition

8. Linked Lists: Some Properties (continued)
current = head;
Copies value of head into current
C++ Programming: Program Design Including Data Structures, Fourth Edition

9. Linked Lists: Some Properties (continued)
current = current->link;
C++ Programming: Program Design Including Data Structures, Fourth Edition

10. Linked Lists: Some Properties (continued)
C++ Programming: Program Design Including Data Structures, Fourth Edition

11. Traversing a Linked List
The basic operations of a linked list are:
Search to determine if an item is in the list
Insert an item in the list
Delete an item from the list
Traversal: given a pointer to the first node of the list, step through the nodes of the list
C++ Programming: Program Design Including Data Structures, Fourth Edition

12. Traversing a Linked List (continued)
To traverse a linked list:
Example:
C++ Programming: Program Design Including Data Structures, Fourth Edition

13. Item Insertion and Deletion
Consider the following definition of a node:
We will use the following variable declaration:
C++ Programming: Program Design Including Data Structures, Fourth Edition

14. Insertion Consider the following linked list:
A new node with info 50 is to be created and inserted after p
C++ Programming: Program Design Including Data Structures, Fourth Edition

16. The sequence of statements to insert the node is very important
The sequence of statements to insert the node is very important. Suppose that we reverse the sequence of the statements and execute the statements in the following order:

17. Deletion
Node with info 34 is removed from the list, but memory is still occupied; node is dangling
C++ Programming: Program Design Including Data Structures, Fourth Edition

19. Building a Linked List (version 1)
This method’s propety: If data is unsorted:
The list will be unsorted
Can build a linked list forward or backward
Forward: a new node is always inserted at the end of the linked list
Backward: a new node is always inserted at the beginning of the list
C++ Programming: Program Design Including Data Structures, Fourth Edition

20. Building a Linked List Forward
You need three pointers to build the list:
One to point to the first node in the list, which cannot be moved
One to point to the last node in the list
One to create the new node
C++ Programming: Program Design Including Data Structures, Fourth Edition

23. Building a Linked List Forward (continued)
We now repeat statements 1 through 6b three more times:
C++ Programming: Program Design Including Data Structures, Fourth Edition

25. Building a Linked List Backward
The algorithm is:
Initialize first to NULL
For each item in the list
Create the new node, newNode
Store the item in newNode
Insert newNode before first
Update the value of the pointer first
C++ Programming: Program Design Including Data Structures, Fourth Edition

27. Linked List as an ADT The basic operations on linked lists are:
Initialize the list
Determine whether the list is empty
Print the list
Find the length of the list
Destroy the list
C++ Programming: Program Design Including Data Structures, Fourth Edition

28. Linked List as an ADT (continued)
The basic operations on linked lists are: (continued)
Retrieve the info contained in the first node
Retrieve the info contained in the last node
Search the list for a given item
Insert an item in the list
Delete an item from the list
Make a copy of the linked list
C++ Programming: Program Design Including Data Structures, Fourth Edition

29. Linked List as an ADT (continued)
In general, there are two types of linked lists:
Sorted and unsorted lists
The algorithms to implement the operations search, insert, and remove slightly differ for sorted and unsorted lists
C++ Programming: Program Design Including Data Structures, Fourth Edition

30. Linked List as an ADT (continued)
If a linked list is unordered, we can insert a new item at either the end or the beginning
buildListForward inserts item at the end
buildListBackward inserts new item at the beginning
To accommodate both operations, we will write two functions:
insertFirst and insertLast
We will use two pointers in the list:
first and last
C++ Programming: Program Design Including Data Structures, Fourth Edition

31. Structure of Linked List Nodes
The node has two member variables
To simplify operations such as insert and delete, we define the class to implement the node of a linked list as a struct
The definition of the struct nodeType is:
C++ Programming: Program Design Including Data Structures, Fourth Edition

32. Member Variables of the class linkedListType
We use two pointers: first and last
We also keep a count of the number of nodes in the list
linkedListType has three member variables:
C++ Programming: Program Design Including Data Structures, Fourth Edition

33. Linked List Iterators
One of the basic operations performed on a list is to process each node of the list
List must be traversed, starting at first node
Common technique is to provide an iterator
Iterator: object that produces each element of a container, one element at a time
The two most common operations are:
++ (the increment operator)
* (the dereferencing operator)
C++ Programming: Program Design Including Data Structures, Fourth Edition

34. Linked List Iterators (continued)
Note that an iterator is an object
We need to define a class (linkedListIterator) to create iterators to objects of the class linkedListType
Would have one member variable:
Refers to (the current) node
C++ Programming: Program Design Including Data Structures, Fourth Edition

35. Good Use for Templates
Since a node can contain anything (not just an int), we want the nodeClass to be templated.
template <class Type>
class nodeType {
private:
Type info;
nodeType<Type> * link };
C++ Programming: Program Design Including Data Structures, Fourth Edition

42. Print the List
C++ Programming: Program Design Including Data Structures, Fourth Edition

43. Length of a List
C++ Programming: Program Design Including Data Structures, Fourth Edition

44. Retrieve the Data of the First Node
C++ Programming: Program Design Including Data Structures, Fourth Edition

45. Retrieve the Data of the Last Node
C++ Programming: Program Design Including Data Structures, Fourth Edition

46. Begin and End
C++ Programming: Program Design Including Data Structures, Fourth Edition

47. Copy the List Steps: Create a node, and call it newNode
Copy the info of the node (in the original list) into newNode
Insert newNode at the end of the list being created
C++ Programming: Program Design Including Data Structures, Fourth Edition

50. Destructor
C++ Programming: Program Design Including Data Structures, Fourth Edition

51. Copy Constructor
C++ Programming: Program Design Including Data Structures, Fourth Edition

52. Overloading the Assignment Operator
C++ Programming: Program Design Including Data Structures, Fourth Edition

54. Search the List
Steps:
Compare the search item with the current node in the list
If the info of the current node is the same as the search item, stop the search
Otherwise, make the next node the current node
Repeat Step 1 until the item is found
Or, until no more data is left in the list to compare with the search item
C++ Programming: Program Design Including Data Structures, Fourth Edition

56. Insert the First Node Steps: Create a new node
Store the new item in the new node
Insert the node before first
Increment count by 1
C++ Programming: Program Design Including Data Structures, Fourth Edition

58. Insert the Last Node
C++ Programming: Program Design Including Data Structures, Fourth Edition

59. Delete a Node Case 1: List is empty Case 2: List is not empty
If the list is empty, output an error message
Case 2: List is not empty
The node to be deleted is the first node
First scenario: List has only one node
C++ Programming: Program Design Including Data Structures, Fourth Edition

60. Delete a Node (continued)
Second scenario: List of more than one node
C++ Programming: Program Design Including Data Structures, Fourth Edition

61. Delete a Node (continued)
Case 3: Node to be deleted is not the first one
Case 3a: Node to be deleted is not last one
C++ Programming: Program Design Including Data Structures, Fourth Edition

62. Delete a Node (continued)
Case 3b: Node to be deleted is the last node
C++ Programming: Program Design Including Data Structures, Fourth Edition

63. Delete a Node (continued)
Case 4: Node to be deleted is not in the list
The list requires no adjustment
Simply output an error message
C++ Programming: Program Design Including Data Structures, Fourth Edition

66. Header File of the Unordered Linked List
C++ Programming: Program Design Including Data Structures, Fourth Edition

67. Header File of the Unordered Linked List (continued)
C++ Programming: Program Design Including Data Structures, Fourth Edition