Chapter 5 - Linked Lists

Introduction

Welcome to the world of linked lists, a must-know data structure that offers flexibility and efficiency that arrays can’t match. If you've ever thought that the way elements are organized in arrays seems a bit rigid, then linked lists will open up a new realm of possibilities for you as a budding hacker. In this chapter, we’ll break down the concept of linked lists, explore their structure, and implement one in C++. Buckle up, because this might just become your favorite data structure!

Understanding Linked Lists

Nodes and Pointers

At the core of linked lists is the node. A node is a fundamental unit that contains two primary components:

• Data: The actual value or information that the node holds. This could be any type of data, such as integers, strings, or even user-defined types.
• Pointer: A reference to the next node in the sequence. This allows linked lists to maintain a dynamic structure since we can easily add or remove nodes.

Here's a basic structure for a node in C++:

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In the code above:

• Node is a struct representing a single element in your linked list.
• data holds the value.
• next is a pointer to the next node, facilitating traversal through the list.

Creating a Linked List: Insertion, Deletion, and Traversal

Insertion

Inserting nodes into a linked list can be done in several ways. Let's look at how to insert nodes at the beginning and at the end.

Inserting at the Beginning

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Inserting at the End

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Deletion

Deleting a node involves updating the pointer of the previous node to point to the node after the one being removed:

Deleting a Node

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Traversal

Traversing through a linked list involves starting from the head and continuing until you reach a node where the pointer to the next node is nullptr.

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Types of Linked Lists

Singly Linked Lists

• A singly linked list has nodes with a single pointer pointing to the next node.
• Memory-efficient, good for applications requiring frequent additions/removals.

Doubly Linked Lists

• A doubly linked list has nodes with two pointers—one pointing to the next node and one to the previous node.
• Allows for easy traversal in both directions but uses more memory.

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Comparing Linked Lists with Arrays

• Size Flexibility: Linked lists can dynamically adjust their size, while arrays have a fixed size.
• Memory Utilization: While arrays may waste memory (unused elements), linked lists only use what they need.
• Access Speed: Arrays allow constant time access (O(1)) to elements, while linked lists require O(n) time to find an element due to traversal.

Exercise and Assignment

1. Implement a Linked List: Write a C++ program to create a singly linked list, and include functions to insert nodes at both the beginning and the end, delete a node, and print the list.

2. Doubly Linked List: Extend the previous exercise by implementing a doubly linked list. Include functionalities to insert and delete nodes, as well as print the list in both directions.

3. Comparative Analysis: Write a short write-up comparing the performance of linked lists versus arrays for a specific use case (e.g., frequent insertions/deletions).

Chapter Summary

Congratulations! You’ve just taken a giant leap into the world of linked lists! You should now have a solid understanding of linked lists, including how to visualize nodes and pointers, perform insertions, deletions, and traversals, and recognize the differences between singly and doubly linked lists versus arrays.

Linked lists are an essential building block for more complex data structures, so keep coding, experimenting, and digging deeper! In the next chapter, we’ll explore stacks and queues—stay tuned!