Before Starting¶
A few years ago, I shared the "Sword for Offer" problem solutions on LeetCode, receiving encouragement and support from many readers. During interactions with readers, the most frequently asked question I encountered was "how to get started with algorithms." Gradually, I developed a keen interest in this question.
Diving straight into problem-solving seems to be the most popular approach—it's simple, direct, and effective. However, problem-solving is like playing Minesweeper: those with strong self-learning abilities can successfully defuse the mines one by one, while those with insufficient foundations may end up bruised and battered, retreating step by step in frustration. Reading through textbooks is also a common practice, but for job seekers, graduation theses, resume submissions, and preparations for written tests and interviews have already consumed most of their energy, making working through thick books an arduous challenge.
If you're facing similar struggles, then it's fortunate that this book has "found" you. This book is my answer to this question—even if it may not be the optimal solution, it is at least a positive attempt. While this book alone won't directly land you a job offer, it will guide you to explore the "knowledge map" of data structures and algorithms, help you understand the shapes, sizes, and distributions of different "mines," and enable you to master various "mine-clearing methods." With these skills, I believe you can tackle problems and read technical literature more confidently, gradually building a complete knowledge system.
I deeply agree with Professor Feynman's words: "Knowledge isn't free. You have to pay attention." In this sense, this book is not entirely "free." In order to live up to the precious "attention" you invest in this book, I will do my utmost and devote my greatest "attention" to completing this work.
I'm acutely aware of my limited knowledge and shallow expertise. Although the content of this book has been refined over a period of time, there are certainly still many errors, and I sincerely welcome critiques and corrections from teachers and fellow students.
Hello, Algorithms!
The advent of computers has brought tremendous changes to the world. With their high-speed computing capabilities and excellent programmability, they have become the ideal medium for executing algorithms and processing data. Whether it's the realistic graphics in video games, the intelligent decision-making in autonomous driving, AlphaGo's brilliant Go matches, or ChatGPT's natural interactions, these applications are all exquisite interpretations of algorithms on computers.
In fact, before the advent of computers, algorithms and data structures already existed in every corner of the world. Early algorithms were relatively simple, such as ancient counting methods and tool-making procedures. As civilization progressed, algorithms gradually became more refined and complex. From the ingenious craftsmanship of master artisans, to industrial products that liberate productive forces, to the scientific laws governing the operation of the universe, behind almost every ordinary or astonishing thing lies ingenious algorithmic thinking.
Similarly, data structures are everywhere: from large-scale social networks to small subway systems, many systems can be modeled as "graphs"; from a nation to a family, the primary organizational forms of society exhibit characteristics of "trees"; winter clothing is like a "stack," where the first item put on is the last to be taken off; a badminton tube is like a "queue," with items inserted at one end and retrieved from the other; a dictionary is like a "hash table," enabling quick lookup of target entries.
This book aims to help readers understand the core concepts of algorithms and data structures through clear and accessible animated illustrations and runnable code examples, and to implement them through programming. Building on this foundation, the book endeavors to reveal the vivid manifestations of algorithms in the complex world and showcase the beauty of algorithms. I hope this book can be of help to you!