# krahets/hello-algo

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122,357 stars · 14,834 forks · Java · other

## Links

- GitHub: https://github.com/krahets/hello-algo
- Homepage: https://www.hello-algo.com
- awesome-repositories: https://awesome-repositories.com/repository/krahets-hello-algo.md

## Topics

`algo` `algorithm` `algorithms` `book` `data-structure` `data-structures` `data-structures-and-algorithms` `dsa` `education` `leetcode` `programming`

## Description

This project is an educational resource and reference library designed to teach fundamental data structures and algorithmic problem-solving. It provides a structured pedagogical framework that organizes complex technical concepts into a logical progression, helping learners understand how data is organized, stored, and processed to solve computational problems efficiently.

The repository distinguishes itself through a multi-language codebase that maintains parallel, consistent implementations of core algorithms and data structures across various programming languages. It bridges the gap between abstract theory and concrete execution by utilizing visual-conceptual mapping, including diagrams and step-by-step walkthroughs, alongside complexity-driven design analysis to evaluate the time and space efficiency of different approaches.

The content covers a broad spectrum of computer science fundamentals, ranging from linear structures like arrays, linked lists, stacks, and queues to complex hierarchical models such as trees, graphs, and hash tables. It also provides deep dives into advanced algorithmic paradigms, including systematic search strategies like backtracking and optimization techniques using dynamic programming.

The materials are designed to serve both as a foundational curriculum for students and as a practical tool for software engineering practitioners preparing for technical assessments. The documentation is structured to allow users to navigate from basic definitions to advanced implementation details, making it a versatile resource for building a strong conceptual foundation in computer science.

## Tags

### Education & Learning Resources

- [Algorithm Fundamentals](https://awesome-repositories.com/f/education-learning-resources/algorithm-fundamentals.md) — Provides a foundational definition and characteristics of algorithms. ([source](https://www.hello-algo.com/chapter_introduction/what_is_dsa/))
- [Computer Science Curricula](https://awesome-repositories.com/f/education-learning-resources/computer-science-curricula.md) — Teaches fundamental data structures and algorithms through structured guides and visual explanations.
- [Data Structure Fundamentals](https://awesome-repositories.com/f/education-learning-resources/data-structure-fundamentals.md) — Defines the core goals and design trade-offs of data structures. ([source](https://www.hello-algo.com/chapter_introduction/what_is_dsa/))
- [Algorithm Repositories](https://awesome-repositories.com/f/education-learning-resources/algorithm-repositories.md) — Provides a comprehensive collection of structured learning materials and code examples.
- [Backtracking Algorithms](https://awesome-repositories.com/f/education-learning-resources/backtracking-algorithms.md) — Provides systematic search strategies for solving complex problems through backtracking methodologies.
- [Computer Science Theory](https://awesome-repositories.com/f/education-learning-resources/computer-science-theory.md) — Explains the fundamental synergy between data structures and algorithms. ([source](https://www.hello-algo.com/chapter_introduction/what_is_dsa/))
- [Data Structure Tutorials](https://awesome-repositories.com/f/education-learning-resources/data-structure-tutorials.md) — 双向队列的实现与队列类似，可以选择链表或数组作为底层数据结构。 ### 1\. 基于双向链表的实现¶ 回顾上一节内容，我们使用普通单向链表来实现队列，因为它可以方便地删除头节点（对应出队操作）和在尾节点后添加新节点（对应入队操作）。 对于双向队列而言，头部和尾部都可以执行入队和出队操作。换句话说，双向队列需要实现另一个对称方向的操作。为此，我们采用“双向链表”作为双向队列的底层数据结构。 如图 5-8 所示，我们将双向链表的头节点和尾节 ([source](https://www.hello-algo.com/chapter_stack_and_queue/deque/))
- [Data Structures](https://awesome-repositories.com/f/education-learning-resources/data-structures.md) — Explains practical applications of deques in scenarios like undo functionality. ([source](https://www.hello-algo.com/chapter_stack_and_queue/deque/))
- [Dynamic Programming](https://awesome-repositories.com/f/education-learning-resources/dynamic-programming.md) — Covers comprehensive dynamic programming techniques, explaining problem characteristics and solution strategies.
- [Algorithms](https://awesome-repositories.com/f/education-learning-resources/algorithms.md) — Details common operations and time complexity for queue data structures. ([source](https://www.hello-algo.com/chapter_stack_and_queue/queue/))
- [Educational Frameworks](https://awesome-repositories.com/f/education-learning-resources/educational-frameworks.md) — Organizes complex technical concepts into a logical progression for students and practitioners.
- [Multi-Language Implementations](https://awesome-repositories.com/f/education-learning-resources/multi-language-implementations.md) — Provides consistent algorithmic logic across multiple programming languages by maintaining parallel source files.
- [Data Structure Implementations](https://awesome-repositories.com/f/education-learning-resources/data-structure-implementations.md) — Provides multi-language code examples for implementing queues using linked lists. ([source](https://www.hello-algo.com/chapter_stack_and_queue/queue/))
- [Backtracking Tutorials](https://awesome-repositories.com/f/education-learning-resources/backtracking-tutorials.md) — Provides a structured walkthrough for solving the N-Queens puzzle using backtracking. ([source](https://www.hello-algo.com/chapter_backtracking/))
- [Dynamic Programming Tutorials](https://awesome-repositories.com/f/education-learning-resources/dynamic-programming-tutorials.md) — Provides a structured walkthrough for solving 0-1 knapsack problems using dynamic programming. ([source](https://www.hello-algo.com/chapter_dynamic_programming/))
- [Educational Curricula](https://awesome-repositories.com/f/education-learning-resources/educational-curricula.md) — Organizes complex technical concepts into independent, hierarchical chapters that allow learners to build knowledge.
- [Knowledge Bases](https://awesome-repositories.com/f/education-learning-resources/knowledge-bases.md) — Offers detailed explanations and complexity analysis for essential computational techniques.
- [Search Algorithms](https://awesome-repositories.com/f/education-learning-resources/search-algorithms.md) — Compares the efficiency of binary search trees against arrays for search operations. ([source](https://www.hello-algo.com/chapter_tree/binary_search_tree/))
- [Stack Data Structures](https://awesome-repositories.com/f/education-learning-resources/stack-data-structures.md) — Details common operations and time complexity for stack data structures. ([source](https://www.hello-algo.com/chapter_stack_and_queue/stack/))
- [Traversal Algorithms](https://awesome-repositories.com/f/education-learning-resources/traversal-algorithms.md) — Explains various tree traversal methods including level-order, pre-order, and post-order. ([source](https://www.hello-algo.com/chapter_tree/binary_tree_traversal/))
- [Tree Data Structures](https://awesome-repositories.com/f/education-learning-resources/tree-data-structures.md) — Defines common terminology for binary trees such as root, leaf, and height. ([source](https://www.hello-algo.com/chapter_tree/binary_tree/))

### Software Engineering & Architecture

- [Data Structures](https://awesome-repositories.com/f/software-engineering-architecture/data-structures.md) — Provides comprehensive guides and implementation details for core array operations and memory management.
- [Software Engineering Principles](https://awesome-repositories.com/f/software-engineering-architecture/software-engineering-principles.md) — Builds a strong conceptual foundation in how data is organized and processed.
- [Complexity Analysis](https://awesome-repositories.com/f/software-engineering-architecture/complexity-analysis.md) — Evaluates data structure performance by comparing time and space efficiency metrics to guide optimal selection.
- [Dynamic Arrays](https://awesome-repositories.com/f/software-engineering-architecture/dynamic-arrays.md) — Outlines implementation principles for dynamic list structures focusing on capacity management and insertion logic.
- [Graph Algorithms](https://awesome-repositories.com/f/software-engineering-architecture/graph-algorithms.md) — Explores graph representation techniques using adjacency matrices and lists with comparative efficiency analysis.
- [Hash Tables](https://awesome-repositories.com/f/software-engineering-architecture/hash-tables.md) — Explains principles of hash table design including collision resolution and algorithmic hashing techniques.
- [Heaps](https://awesome-repositories.com/f/software-engineering-architecture/heaps.md) — Covers heap-based priority queue operations, construction methods, and complexity analysis.
- [Linked Lists](https://awesome-repositories.com/f/software-engineering-architecture/linked-lists.md) — Provides a comparative analysis of singly, doubly, and circular linked list structures.
- [Queue Implementations](https://awesome-repositories.com/f/software-engineering-architecture/queue-implementations.md) — Details operational strategies and implementation techniques for double-ended queues.
- [Queues](https://awesome-repositories.com/f/software-engineering-architecture/queues.md) — Defines standard queue operations and implementation strategies using linear structures.
- [Stacks](https://awesome-repositories.com/f/software-engineering-architecture/stacks.md) — Explains the operational mechanics of stacks and their utility in memory management.
- [Trees](https://awesome-repositories.com/f/software-engineering-architecture/trees.md) — Covers hierarchical data structure concepts including binary tree traversal and search properties.
- [Abstract Data Types](https://awesome-repositories.com/f/software-engineering-architecture/abstract-data-types.md) — Defines core operations and constraints for data structures to separate logical behavior from specific memory-based implementation details.

### Development Tools & Productivity

- [Algorithm Libraries](https://awesome-repositories.com/f/development-tools-productivity/algorithm-libraries.md) — Provides a curated library of efficient, multi-language implementations for classic algorithms.
- [Interview Preparation](https://awesome-repositories.com/f/development-tools-productivity/interview-preparation.md) — Covers common coding interview topics and problem-solving patterns.

### Programming Languages & Runtimes

- [Multi-Language Implementations](https://awesome-repositories.com/f/programming-languages-runtimes/multi-language-implementations.md) — Provides implementations of core algorithms and data structures across a wide variety of programming languages.