Linked Lists: Types and Implementations

Singly Linked List

A singly linked list is the simplest kind. Each node has two parts: the data (like a number or word) and a pointer that shows the way to the next node. The last node points to nothing (null), telling you the list is over.

Think of it like a one-way road—you can only move forward. Adding a new node is quick if you’re at the start, but it takes more steps to reach the end. You might use this in a program where you only need to go one direction, like tracking scores in a game. For a deeper dive into these concepts, check out some essential DSA courses.

Here’s what makes singly linked lists special:

• One pointer per node, keeping it simple.
• Great for moving forward through data.
• Takes less memory than other types.

Doubly Linked List

A doubly linked list steps things up a bit. Each node still has data, but now it has two pointers—one to the next node and one to the previous node. It’s like a two-way street where you can go forward or backward.

This makes some tasks easier, like removing a node, because you can find its neighbors fast. It’s perfect for things like a music app where you want to skip back to the last song. If you’re prepping for a big tech interview, like at Amazon, mastering this could help—see these Amazon DSA Questions for practice.

Key features of doubly linked lists:

• Two pointers let you travel both ways.
• Easier to delete or rearrange nodes.
• Uses more memory because of the extra pointer.

Circular Linked List

A circular linked list is a fun twist. Instead of ending with a null pointer, the last node loops back to the first one, making a circle. It can be singly (one-way) or doubly (two-way), depending on what you need.

Picture a merry-go-round—it keeps going around without a clear start or stop. This is awesome for things like a playlist that repeats or a game where players take turns in a loop. Curious about real-world uses? Explore more in a crash course on data structures.

What sets circular linked lists apart:

• No end—just keeps circling back.
• Handy for repeating patterns or cycles.
• Needs careful handling to avoid getting stuck in a loop.

Implementations of Linked Lists

Now that we know the types, let’s see how to build them. We’ll use Python because it’s easy to read, but the ideas work in any language. Each type needs a node class and a list class to manage it.

Implementing a Singly Linked List

For a singly linked list, you start with a node that holds data and a next pointer. Then, you make a class to control the whole list—like adding or removing nodes.

Here’s a simple setup in Python:

class Node: