Linked Lists

A High School & College Primer to Nodes, Pointers, and the Algorithms That Use Them

Your professor just put linked lists on the exam, your textbook chapter is forty pages long, and your exam is in two days. This guide cuts straight to what you need.

**TLDR: Linked Lists** is a focused, 10–20 page primer that walks you through everything from the basic node-and-pointer mental model to the classic interview techniques — reversing a list, the two-pointer trick, and Floyd's cycle detection. Along the way you'll see exactly how linked lists trade off against arrays in memory layout and Big-O performance, how singly and doubly linked lists differ, and where these structures actually show up in real software (queues, LRU caches, hash table buckets, and more).

This guide is written for AP Computer Science students, college freshmen and sophomores in intro CS courses, and anyone doing coding interview data structures prep who wants a clean, honest explanation without a 500-page commitment. Every operation comes with worked code and pointer diagrams. Every common misconception is named and corrected. No filler, no padding — just the concepts you need to feel oriented and confident.

If your next class, exam, or technical interview involves linked lists, read this first.

What you'll learn

Explain what a linked list is and how nodes and pointers connect to form one.
Compare linked lists to arrays in terms of memory layout, access time, and insertion/deletion cost.
Implement core operations — insert, delete, search, traverse — on a singly linked list.
Distinguish singly, doubly, and circular linked lists and pick the right variant for a problem.
Apply classic linked-list techniques like two pointers, reversal, and cycle detection.

What's inside

1. What Is a Linked List?

Introduces nodes, pointers, and the head reference, and contrasts the chain-of-nodes mental model with arrays.
2. Linked Lists vs. Arrays: Memory and Trade-offs

Explains why linked lists exist by comparing their memory layout and Big-O performance to arrays for common operations.
3. Core Operations on a Singly Linked List

Walks through traversal, search, insertion at head/middle/tail, and deletion with code and pointer diagrams.
4. Doubly and Circular Linked Lists

Introduces variants with prev pointers and looped tails, and shows when each variant earns its extra complexity.
5. Classic Linked-List Techniques

Teaches three high-yield patterns: reversing a list, the two-pointer (slow/fast) technique, and Floyd's cycle detection.
6. Where Linked Lists Show Up

Surveys real uses — stacks, queues, hash table buckets, LRU caches, and adjacency lists — and gives guidance on when to reach for one.

Published by Solid State Press

TLDR STUDY GUIDES

Linked Lists

A High School & College Primer to Nodes, Pointers, and the Algorithms That Use Them

Solid State Press

Linked Lists

A High School & College Primer to Nodes, Pointers, and the Algorithms That Use Them

Published by Solid State Press.

Part of the TLDR Study Guides series.

Who This Book Is For

If you are a high school student looking for an AP Computer Science linked list review, a college freshman working through computer science concepts for college freshmen in an intro CS course, or a self-taught coder trying to make sense of nodes and pointers explained from scratch, this book was written for you. It also works for tutors, parents, and anyone who learns best by seeing the logic before the syntax.

This is a data structures study guide for high school and early college level. It covers how linked lists store data in memory, the linked list vs. array when-to-use decision, singly and doubly linked lists, core operations (insert, delete, traverse, reverse), classic techniques like the two-pointer method, and a linked list tutorial for beginners that builds toward coding interview data structures prep. About 15 focused pages — no filler, no padding.

Read it straight through once, work every example as you go, then tackle the problem set at the end to confirm you have it.

1 What Is a Linked List?
2 Linked Lists vs. Arrays: Memory and Trade-offs
3 Core Operations on a Singly Linked List
4 Doubly and Circular Linked Lists
5 Classic Linked-List Techniques
6 Where Linked Lists Show Up

Chapter 1

What Is a Linked List?

Imagine you need to store a list of five numbers. The obvious move is an array: five slots in a row, each holding one number. But what if you need to insert a new number in the middle? You shift everything to the right to make room. For five numbers that's fine. For five million, it costs real time. A linked list solves insertion and deletion differently — not by rearranging data, but by changing which pieces of data point to which.

The Node: The Basic Unit

A node is a small container that holds two things: a piece of data and a way to find the next node. That "way to find the next node" is called a pointer (in lower-level languages like C) or a reference (in higher-level ones like Java or Python). The words are used interchangeably in most CS courses, and throughout this book "pointer" and "reference" mean the same thing.

Concretely, every node has two fields:

The data field stores the actual value — an integer, a string, whatever the list is meant to hold.
The next field stores a reference to the next node in the sequence. If there is no next node, this field is set to null (sometimes written None in Python or nullptr in C++). Null simply means "this pointer points to nothing; the chain ends here."

In Python-style pseudocode, a node class looks like this:

class Node:
    def __init__(self, data):
        self.data = data   # data field
        self.next = None   # next field, null by default

That's it. Two fields. Everything else about a linked list is just a collection of these nodes wired together.

Chaining Nodes Into a List

You build a linked list by pointing one node's next field at another node. The result is a chain:

[10 | •]——>[25 | •]——>[7 | •]——>[41 | null]

Each box is a node. The left half is the data; the right half (the dot with an arrow) is the next pointer. The last node's next is null — that's how you know you've reached the end.

Keep reading

You've read the first half of Chapter 1. The complete book covers 6 chapters in roughly fifteen pages — readable in one sitting.

Coming soon to Amazon