What is a linked list in Python?

Table of Contents

• Introduction
• What is a Linked List?
  • Types of Linked Lists
• Implementation Examples in Python
  • 1. Singly Linked List
  • 2. Doubly Linked List
  • 3. Circular Linked List
• Advantages of Linked Lists
• Use Cases
• Conclusion

Introduction

A linked list is a fundamental data structure used to store a collection of elements. Unlike arrays or lists, which store elements in contiguous memory locations, a linked list stores elements in nodes where each node points to the next (and possibly previous) node. This structure allows for efficient insertion and deletion operations.

What is a Linked List?

A linked list consists of a sequence of nodes, where each node contains:

• Data: The value or information stored in the node.
• Pointer/Reference: A reference to the next node in the sequence (and possibly to the previous node, depending on the type of linked list).

Types of Linked Lists

1. Singly Linked List
   • Each node has a reference to the next node.
   • The list is traversed from the head node to the end (null reference).
2. Doubly Linked List
   • Each node has references to both the next and previous nodes.
   • Allows traversal in both directions, from head to tail and vice versa.
3. Circular Linked List
   • The last node points back to the first node, creating a circular structure.
   • Can be singly or doubly linked.

Implementation Examples in Python

1. Singly Linked List

A singly linked list is implemented by defining a Node class and a LinkedList class that manages the nodes.

Example:

2. Doubly Linked List

A doubly linked list is similar to a singly linked list but each node also has a reference to the previous node.

Example:

3. Circular Linked List

In a circular linked list, the last node points back to the first node, forming a circle.

Example:

Advantages of Linked Lists

• Dynamic Size: Can grow or shrink in size dynamically, unlike arrays.
• Efficient Insertions/Deletions: Insertions and deletions are more efficient compared to arrays, especially when inserting/removing elements from the middle.

Use Cases

• Dynamic Memory Allocation: When the number of elements is not known in advance.
• Implementing Other Data Structures: Used as building blocks for more complex data structures such as stacks, queues, and hash tables.

Conclusion

A linked list is a versatile data structure in Python that offers dynamic sizing and efficient insertions and deletions. Depending on the needs of your application, you can implement singly, doubly, or circular linked lists to manage your data effectively. Understanding the types and their implementations helps in choosing the right data structure for various programming tasks.