Reverse a Linked List in Python (Step-by-Step) | Store-Todo-Jodo-Aage Badho Trick | Dry Run & Code

Reversing a Singly Linked List is a classic interview question that often confuses beginners. The logic of moving pointers can feel like a game of musical chairs where someone always ends up falling off!

To make this simple, we use a foolproof four-step mental model: Store, Todo, Jodo, and Aage Badho. ### The Core Logic Before we dive into the code, imagine you are standing at a node. To reverse the list without losing your data, you must follow this rhythm:

1. Store: Save the address of the next node so you don’t lose the rest of the list.

2. Todo (The Task): Change the current node’s pointer to point backwards to the previous node.

3. Jodo (The Link): Move your “Previous” marker to the current node.

4. Aage Badho (Move Forward): Jump to the “Stored” next node and repeat.

Code Implementation :

Here is how we translate that intuition into clean Python code.

def reverse_list(head):
    prev = None
    curr = head
    
    while curr:
        # 1. Store (Save the next node)
        next_node = curr.next 
        
        # 2. Todo (Reverse the link)
        curr.next = prev 
        
        # 3. Jodo (Update previous)
        prev = curr 
        
        # 4. Aage Badho (Move to the saved next node)
        curr = next_node 
        
    return prev  # New head of the reversed list

Let’s undestand the above code by dry run

Linked list : 1 → 2 → 3 → 4 → None

So, Final answer you will get : 4 → 3 → 2 → 1 → None

Still confused, then watch the full explanation (Step-by-Step)

👉 I’ve explained this entire concept visually on my YouTube channel:

🔗Youtube

Get the Full Source Code

Building a Linked List requires more than just the reverse function. You need the Node class and the LinkedList wrapper. We have compiled the complete, ready-to-run script—including insertion and display methods—on GitHub.

📁 Access the Full Source Code on GitHub

Key Takeaways for Exams

• Time Complexity: O(n), where n is the number of nodes. We visit each node exactly once.

• Space Complexity: O(1), as we are only using a few pointer variables regardless of the list size.

• Pro-Tip: Always handle the edge case where the list is empty or has only one node!

Still have doubts? Check these commonly asked questions:

1. Can we implement Linked Lists in other languages?

Yes, absolutely! While we used Python here, the logic of Store → Todo → Jodo → Aage Badho is universal. In C++ or Java, you would use pointers or references to achieve the same result. The only difference is the syntax; the logic remains the same.

2. Can we build a real project using only a Single Linked List?

Yes! Linked lists are the backbone of many systems. You can create projects like:

• A Music Playlist Manager: Where each song is a node pointing to the next.

• An Undo/Redo System: Using a linked list to track history.

• A Student Management System: Efficiently adding or removing student records without shifting an entire array.

3. What is the real-world application of reversing a Linked List?

In a real-world scenario, you might reverse a list to:

• Reverse a browser’s navigation history.

• Process tasks in Last-In, First-Out (LIFO) order when you only have access to a forward-pointing list.

• Prepare data for specific algorithms (like checking if a linked list is a palindrome).

4. Why is this question so popular in technical interviews?

Interviewers love this question because it tests your pointer manipulation skills and your ability to keep track of memory without losing data. If you can reverse a list without making a “dangling pointer” error, it shows you have a strong grasp of data structures.

5. Is there a recursive way to reverse a Linked List?

Yes! While we used the iterative (loop) approach here because it is more memory-efficient O(1) space, you can also reverse a list using recursion. However, for large lists, the iterative method is usually preferred to avoid stack overflow.

6. What is the biggest mistake beginners make?

Most common mistakes:

• Forgetting to store next node
• Losing reference to the list
• Incorrect pointer updates

 That’s why the method
Store → Todo → Jodo → Aage Badho is very powerful.

 What’s Next? Practice With Me!

Now that you’ve understood how to reverse a linked list using  Store → Todo → Jodo → Aage Badho. It’s time to level up

Next Problem:  Find the middle element of a Linked List using the 2-pointer (slow & fast) approach

This is another very important interview question and builds directly on what you learned here.

🎯 Build a Real Project (Don’t Stop at Theory!)

If you really want to master Linked Lists, don’t just solve problems — build something real.

👉 I’ve created a complete project using only:

• Singly Linked List
• Basic operations (insert, delete, reverse, traversal)

🔗 [Click here to explore the full project]

This will help you:

• Understand real-world use cases
• Strengthen DSA concepts
• Prepare for interviews + projects