How to Reverse a Linked List in Python

This guide explains how to complete the reverse method to fully reverse a linked list in Python. Learn how to implement the reverse operation effectively with a step-by-step guide.
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How to Reverse a Linked List in Python
Reversing a linked list is a common problem you might encounter in programming, especially while dealing with data structures and algorithms. This guide will guide you through the implementation of the reverse operation in a linked list using Python.
Understanding the Concept
A linked list is a data structure consisting of a collection of nodes which together represent a sequence. Each node contains two fields: a data value and a reference (or link) to the next node in the sequence. To reverse a linked list means to reverse the direction of the links between nodes so that the last node becomes the first, and the first node becomes the last.
Steps to Reverse a Linked List
In order to reverse a linked list, you need to iterate through the linked list and reverse the pointers. Here's a step-by-step guide for the implementation:
Initialize three pointers: prev, curr, and next.
prev (previous) pointer will initially be set to None.
curr (current) pointer will initially point to the head of the list.
next pointer will be used to temporarily store the reference to the next node.
Iterate through the linked list:
Store the next node.
Reverse the current node's pointer to the previous node.
Move the prev and curr pointers one step forward.
Update the head of the list to the prev pointer once the list is fully reversed.
Here is the code implementation:
[[See Video to Reveal this Text or Code Snippet]]
Explanation of the Code
Initialization: We create a class Node to define the structure of each node. The reverse_linked_list function is then defined which takes the head of the list as input.
While Loop: We iterate through the list using a while loop until curr becomes None. Inside the loop:
next_node stores the reference to the next node (curr.next).
curr.next is updated to point to prev, reversing the link.
prev is then moved to curr, and curr is moved to next_node.
Head Update: Finally, after the loop ends, we update the head of the linked list to prev, which now points to the last (or new first) node of the reversed linked list.
Conclusion
Reversing a linked list is a straightforward operation once you understand the process of reassigning the node pointers. This method of reversing is efficient and works well for singly linked lists. Hopefully, this guide helps you thoroughly understand how to implement the reverse operation on a linked list in Python.
Have fun coding and exploring more about linked lists and their various operations!