TheAlgorithms C-Plus-Plus: An Educational Collection of C++ Algorithm Implementations

What the Repository Contains and Who It Is For

TheAlgorithms/C-Plus-Plus is a collection of algorithm implementations written in C++ for educational purposes. The README describes it as spanning topics from computer science, mathematics and statistics, data science, machine learning, and engineering. The stated purpose is to provide a learning resource for educators and students, with implementations and documentation meant to explain mechanisms rather than optimize for production throughput.

The audience is clearly defined by this scope. A student learning how binary search trees work can find an implementation in the data_structures/ folder and read through it without needing to install any library or configure any dependency. An educator can reference a specific file in class or link to the online documentation, which is generated directly from the source code. Engineers looking for algorithm code to drop into a production system will find the implementations informative but likely unsuitable as-is, since they prioritize clarity over performance tuning and carry no API stability guarantee.

The collection includes implementations of the same algorithm in multiple variants when different strategies or optimizations exist. The README notes that one may find more than one implementation for the same objective, which makes it more useful for comparison learning than as a definitive reference.

Directory Structure and How Algorithms Are Organized

The repository's top-level directories map directly to algorithm categories. The visible folders include: backtracking, bit_manipulation, ciphers, cpu_scheduling_algorithms, data_structures, divide_and_conquer, dynamic_programming, games, geometry, graph, graphics, greedy_algorithms, hashing, machine_learning, math, numerical_methods, operations_on_datastructures, others, physics, probability, range_queries, search, sorting, and strings.

This organization means finding an implementation requires knowing which category the algorithm belongs to. Sorting algorithms are under sorting/, tree traversal is under data_structures/, numerical root-finding methods are under numerical_methods/, and cryptographic cipher implementations are under ciphers/. The DIRECTORY.md file at the repository root provides an index of all files, which is the fastest way to locate a specific algorithm without browsing individual folders.

The doc/ folder at the root contains assets for the Doxygen-generated documentation. The online documentation at TheAlgorithms.github.io/C-Plus-Plus is generated from the source code itself and includes code snippets, program flow diagrams, and links to C++ STL documentation for the library functions each implementation uses. Clicking the Files menu on the documentation site lists every documented file in the collection.

How to Browse, Clone, and Run the Implementations

The simplest way to access the collection is the online documentation at https://TheAlgorithms.github.io/C-Plus-Plus, which provides a browsable interface with syntax-highlighted code and diagrammatic program flow representations.

For local use, cloning the repository gives direct access to every source file. The repository includes a CMakeLists.txt at the root, which is the build configuration for compiling the implementations. Each source file is designed to be compiled independently without linking any external library. The README states that each source code is atomic using STL classes and no external libraries are required for their compilation and execution.

Every implementation includes a self-check mechanism. This means running the compiled binary verifies the implementation against known inputs and outputs. The README states that these self-checks ensure correct implementations with confidence. This design makes it straightforward to verify that an implementation produces expected results on your compiler and platform before studying or adapting it.

C++17 Standard and the No-External-Libraries Constraint

The entire collection adheres to C++17, which the README notes ensures portability to embedded systems such as the ESP32 and ARM Cortex platforms with little to no changes. This is a concrete commitment, not a general statement: every implementation must compile under C++17 without relying on features from later standards or from third-party libraries.

The exclusive use of the Standard Template Library has a direct educational benefit. When a student reads an implementation of, say, a merge sort or a shortest-path algorithm, they see exactly what the algorithm does without the algorithm's logic being obscured by library function calls. The documentation links STL function names to their official cppreference entries, making it possible to understand both the algorithm and the language constructs it uses in the same reading session.

This constraint is also a trade-off. Production algorithm libraries such as Boost or Intel's oneTBB include parallelism, SIMD optimizations, and error handling that would not be appropriate in educational implementations. A developer porting code from this repository to a high-throughput context will need to add those concerns manually.

How Implementations Are Tested and Documented

The repository runs a CI workflow called "Awesome CI Workflow" that compiles and tests every source file on the latest versions of three operating systems: Windows using MSVC 19 2022, macOS using AppleClang 15.0.15, and Ubuntu (Linux) using GNU 13.3.0. This means any implementation that fails to compile or fails its self-check on any of these compilers is caught before it merges into the master branch.

The CodeQL analysis workflow provides additional static analysis coverage. A Gitpod configuration at the repository root allows running the repository in a browser-based IDE without local setup, which lowers the barrier for contributors and students who do not have a local C++ development environment.

Documentation is generated with Doxygen from inline comments in each source file. The documentation site includes interactive source code views with links to the documentation for every STL function used, which is a specific design choice to make the implementations self-explanatory. The documentation license is CC BY-SA 4.0, separate from the MIT license that covers the source code.

Limitations: Educational Scope and What This Repository Is Not

The README is explicit that implementations are meant to provide a learning resource, not a production library. This means several things in practice. There is no semantic versioning, no stable API contract, and no guarantee that a specific implementation will not change between commits. An engineer who pins a dependency on a specific file from this repository will need to re-validate it after any upstream changes.

The multiple-implementation design, which is a feature for learning, can be a problem for selection: when a folder contains three implementations of the same algorithm, the repository does not indicate which is preferred for general use. The variations exist to illustrate different approaches, and choosing among them requires reading the code rather than consulting a recommendation.

Performance benchmarks are not included. The README does not claim any implementation is fast, and benchmarks comparing these implementations against each other or against standard library equivalents are not part of the project.

TheAlgorithms C-Plus-Plus Compared to cppreference.com

cppreference.com is a reference for the C++ language standard and the standard library. It documents what each STL function does, what complexity guarantees it provides, and what edge cases to handle. It is authoritative for language semantics and library specifications, but it does not provide standalone implementations of algorithms that are not in the standard library.

TheAlgorithms/C-Plus-Plus occupies a different position. It provides implementations of algorithms that are not in the STL, such as specific graph traversal algorithms, machine learning models, cipher implementations, and numerical methods. It also provides re-implementations of concepts that are in the STL (like sorting algorithms) as educational material to show how those algorithms work internally, rather than as alternatives to the standard library for production use.

The two resources are complementary. A student learning about Dijkstra's algorithm would use this repository to see a working C++ implementation with self-checks, and would use cppreference to understand the STL containers (priority_queue, unordered_map) that the implementation uses.

License, Contributing, and Current Status

The source code is licensed under the MIT License. The documentation at TheAlgorithms.github.io/C-Plus-Plus is licensed separately under CC BY-SA 4.0, which requires attribution and sharing of derivatives under the same license. Contributors should read the CONTRIBUTING.md and CodingGuidelines.md files at the repository root before submitting new implementations.

The last push to TheAlgorithms/C-Plus-Plus was on 2026-09-21. The repository has no GitHub releases, which is consistent with a continuously updated collection rather than a versioned software product. New algorithm submissions and corrections are merged on an ongoing basis according to the contribution guidelines.

The REVIEWER_CODE.md file at the repository root documents the criteria that reviewers apply when evaluating pull requests, which gives contributors a clear target for what an acceptable implementation looks like.

Editorial conclusion

Students and educators who want readable, self-contained C++ implementations of standard algorithms will find this repository directly usable. It is a poor fit for engineers who need production-ready algorithm code with performance guarantees, API stability, or integration with a build system beyond CMake. Before using any implementation in a non-educational context, review the MIT license terms and verify that the self-check in the implementation covers your edge cases, since the collection is designed for understanding, not for production contracts.

Frequently asked questions

Official sources

1. Official documentation
2. Official README
3. Project repository