C++ programming program design including data structure 7th ch16

Chapter 16:
Linked Lists


Objectives

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In this chapter, you will:

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Learn about linked lists
Become familiar with 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 implement linked lists as ADTs

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Objectives (cont’d)

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Learn how to create linked list iterators
Learn how to implement the basic operations on a linked list
Learn how to create unordered linked lists
Learn how to create ordered linked lists
Learn how to construct a doubly linked list
Become familiar with circular linked lists

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Introduction

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Data can be organized and processed sequentially using an array, called a sequential list
Problems with an array

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Array size is fixed

Unsorted array: searching for an item is slow
Sorted array: insertion and deletion is slow because it requires data movement

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Linked Lists

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Linked list: a collection of items (nodes) containing two components:

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Data
Address (link) of the next node in the list

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Linked Lists (cont’d.)

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Example:

– Link field in the last node is nullptr

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Linked Lists (cont’d.)

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A node is declared as a class or struct

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Data type of a node depends on the specific application
Link component of each node is a pointer

Variable declaration:

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Linked Lists: Some Properties

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Example: linked list with four nodes (Figure 16-4)

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Linked Lists: Some Properties (cont’d.)

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current = head;

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Copies value of head into current

C++ Programming: Program Design Including Data Structures, Seventh Edition

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Linked Lists: Some Properties (cont’d.)

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current = current->link;

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Traversing a Linked List

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Basic operations of a linked list:

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Search for an item 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

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Traversing a Linked List (cont’d.)

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To traverse a linked list:

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Example:

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Item Insertion and Deletion

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Definition of a node:

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Variable declaration:

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Insertion

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To insert a new node with info 50 after p in this list:

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Insertion (cont’d.)

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Insertion (cont’d.)

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Can use two pointers to simplify the insertion code somewhat:

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To insert newNode between p and q:

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Insertion (cont’d.)

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Deletion

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Node with info 34 is to be deleted:

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Deletion (cont’d.)

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Node with info 34 is removed from the list, but memory is still occupied

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Node is dangling

Must keep a pointer to the node to be able to deallocate its memory

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Deletion (cont’d.)

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Building a Linked List

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If data is unsorted, the list will be unsorted
Can build a linked list forward or backward

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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

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Building a Linked List Forward

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Need three pointers to build the list:

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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

Example:

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Data: 2 15 8 24 34

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Building a Linked List Forward (cont’d.)

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Building a Linked List Forward (cont’d.)

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Building a Linked List Forward (cont’d.)

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Now repeat this process three more times:

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