# aalhour/C-Sharp-Algorithms: a reference library of classic data structures in C#

> The repository ships 35+ data structures and 40+ algorithms as separate C# projects targeting .NET 10.0, with 623 unit tests. It is a teaching and reference codebase, not a production dependency.

**aalhour/C-Sharp-Algorithms** — :books: :chart_with_upwards_trend: Plug-and-play class-library project of standard Data Structures and Algorithms in C#

- Repository: https://github.com/aalhour/C-Sharp-Algorithms
- Stars: 6,165 · Forks: 1,392
- Language: C#
- License: MIT
- Published: 2026-09-22 · Updated: 2026-09-22 · Language: en
- Canonical page: https://hysenlabs.com/projects/aalhour-c-sharp-algorithms

## What aalhour/C-Sharp-Algorithms is for

Most C# developers reach for the BCL when they need a dictionary, a sorted set or a priority queue. That covers the common cases and it is the right default. The gap this repository fills is narrower: it is a set of readable implementations of structures the BCL does not expose, and of algorithms that appear in interviews and coursework. The README describes the project as having "started as interview prep" and evolved into a reference implementation. That origin explains the shape of the codebase. Every structure lives in its own file with a name that matches the textbook term, so a reader looking for separate chaining can open ChainedHashTable.cs and read the collision logic directly rather than inferring it from an abstraction.

The audience is therefore specific. It suits a developer studying for a data structures interview in C#, an instructor who wants working source to walk through in class, or an engineer who needs to understand how a binomial heap or a cuckoo hash table behaves before choosing a library that hides it. It does not suit someone who wants a drop-in replacement for System.Collections.Generic. The README frames the components as educational first, and that ordering is honest about the trade-off.

## How the repository is split and what each project holds

The solution file C-Sharp-Algorithms.sln ties together three projects. Algorithms/ contains sorting, searching and graph algorithms. DataStructures/ contains the containers. UnitTest/ holds the test coverage, which the README counts at 623+ unit tests. That three-way split is the whole architecture; there is no runtime service, no plugin loader and no configuration layer.

Within DataStructures/ the layout is by category. Lists/ holds ArrayList, Stack, Queue, SLinkedList, DLinkedList, SkipList and CircularBuffer. Heaps/ holds BinaryMinHeap, BinaryMaxHeap, BinomialMinHeap, MinPriorityQueue and KeyedPriorityQueue. Dictionaries/ holds four hash table variants: ChainedHashTable for separate chaining, CuckooHashTable, OpenScatterHashTable for linear probing, and OpenAddressingHashTable for double hashing. Hashing/ holds PrimeHashingFamily and UniversalHashingFamily, which are the hash function families the tables draw on. Trees/ splits again into search trees (BinarySearchTree, AugmentedBinarySearchTree, TernarySearchTree), self-balancing trees (AVLTree, RedBlackTree, BTree) and prefix trees (Trie, TrieMap). Graphs/ is organised on two axes: directed or undirected, weighted or unweighted, and sparse or dense, giving eight concrete graph classes such as UndirectedWeightedSparseGraph and DirectedDenseGraph.

That graph matrix is the clearest design decision in the repository. Rather than one graph type with an internal representation flag, the author wrote a separate class per combination. It is more code to navigate, but each class can be read on its own terms, and the adjacency-list versus adjacency-matrix trade-off becomes visible in the type name.

## Building the solution and running your first traversal

The README gives a Quick Start that requires the .NET 10.0 SDK or later. There is no package to install from a feed in the documented path; the instructions clone the repository and build it locally.

```bash
git clone https://github.com/aalhour/C-Sharp-Algorithms.git
cd C-Sharp-Algorithms
dotnet build
dotnet test
```

The build compiles the three projects in the solution. The test command runs the UnitTest project, which the README counts at 623+ tests; a clean run should report all of them passing. If the SDK on your machine is older than 10.0, the build fails at restore time rather than at compile time, so check `dotnet --version` first.

To use a structure in your own code you reference the DataStructures project from your solution and construct the class directly. The README's graph table is the entry point for traversal work: pick the class matching your graph's shape, for example DirectedWeightedSparseGraph for a weighted directed graph stored as adjacency lists, then call the traversal and shortest-path routines from Algorithms/. The README does not spell out the exact method signatures for those calls, so the first real step after a successful build is to open the graph class and the corresponding algorithm file side by side. That is the intended workflow for this repository, and it is why the classes are kept small and individually named.

## Where the library stops being the right choice

The most visible limitation is packaging. The repository has a Nuget/ directory at the top level, but the README's Quick Start does not mention installing a package, and no package identifier or install command appears in the README. If you want this code in a product, plan on referencing the projects from source or building your own package. That means you own the upgrade path, including any breaking change the author makes between releases.

Version history reinforces the point. The releases listed are v2.0.1 and v2.0.0 in January 2026, preceded by v1.0 in December 2019. A six-year gap between v1.0 and v2.0.0 is a signal about cadence: this is not a library that tracks fast-moving platform changes on a tight schedule. The jump to .NET 10.0 in the current README is a large one, and any code you wrote against the 2019 API should be assumed to need review rather than a version bump.

The second limitation is scope discipline. These are classic structures implemented for clarity. The README describes the project as educational and the components as readable, modular and tested. Nothing in the README claims thread safety, allocation guarantees, or performance parity with the BCL. For a hot path in a server, System.Collections.Generic and the built-in sorting routines remain the correct answer. Use this repository when understanding the mechanism matters more than the constant factor, and treat any structure you lift into production as code you now maintain.

## How this differs from a general-purpose C# collections library

The obvious alternative is the .NET Base Class Library itself. Dictionary, HashSet, SortedDictionary, Stack and Queue cover the everyday containers, and the BCL implementations are the ones you should ship. The difference in approach is that the BCL is optimised and abstracted: you get a Dictionary and you do not choose between separate chaining and double hashing. This repository makes that choice explicit by offering ChainedHashTable, CuckooHashTable, OpenScatterHashTable and OpenAddressingHashTable as four separate types. If your goal is to reason about collision behaviour, the BCL gives you nothing to read and this repository gives you four files.

A second comparison point is the algorithm surface. The BCL does not ship a red-black tree, an AVL tree, a binomial heap, a skip list or a trie as public types, and it does not expose graph traversal at all. That is the territory this project occupies. Where a mature third-party collection library would give you one tuned hash map and one tuned priority queue, this project gives you the family of variants and the hashing functions behind them, at the cost of having no package feed, no semantic-versioning promise beyond the tags listed, and no documented support policy.

## Licence, maintenance and what an upgrade actually costs

The repository is MIT licensed, and the README carries a licence badge pointing at the LICENSE file. MIT is permissive: it allows use, modification and redistribution provided the copyright notice and permission notice are retained. That is the practical implication for anyone vendoring the source into a product. This is a description of the licence text, not legal advice; if your organisation has a policy on attribution or on bundled third-party code, run the LICENSE file past whoever owns that policy before you copy files into your tree.

On maintenance, the last push was on 2026-09-17, and the repository is not archived. The release tags tell the longer story: v1.0 in December 2019, then v2.0.0 and v2.0.1 in January 2026. So the project is alive, but its release cadence is measured in years, not months. The upgrade cost follows from that. Because there is no documented package install, upgrading means pulling the source and reconciling it with whatever local modifications you made, which is the expensive part of vendoring. If you only ever read the code and never copy it, the upgrade cost is zero and the cadence does not matter.

## Conclusion

Adopt this repository if you need readable C# source for AVL trees, red-black trees, cuckoo hashing or graph traversal and you are willing to read the code rather than call a package. Do not adopt it as a runtime dependency in a shipping product: there is no documented NuGet install path, so you would be vendoring source you must then maintain. Before you commit, verify two things in the repository itself: whether the Nuget/ directory contains a packaged artifact you can reference, and how the UnitTest project is wired into your own test run. The algorithms are the product here, and the product is meant to be read.

## FAQ

### Is aalhour/C-Sharp-Algorithms a NuGet package I can install?

The README's Quick Start does not document a package install; it tells you to clone the repository and run dotnet build and dotnet test. The repository does contain a top-level Nuget/ directory, but the README gives no package identifier or install command, so verify that directory yourself before assuming a feed exists.

### What .NET version does aalhour/C-Sharp-Algorithms require?

The README states the requirement as the .NET 10.0 SDK or later, and the repository carries a .NET 10.0 badge. The solution also includes a global.json file at the top level, which is where the SDK version pin would live.

### What data structures and algorithms does aalhour/C-Sharp-Algorithms include?

The README advertises 35+ data structures and 40+ algorithms across lists, heaps, hash tables, trees and graphs. Concrete examples named in the README include AVLTree, RedBlackTree, BTree, Trie, SkipList, BinaryMinHeap, BinomialMinHeap, CuckooHashTable and eight graph classes split by directedness, weighting and density.

### Is aalhour/C-Sharp-Algorithms still maintained?

The repository is not archived and the last push was on 2026-09-17. The release tags show v1.0 in December 2019 followed by v2.0.0 and v2.0.1 in January 2026, so releases are infrequent even though the repository has recent activity.

## Sources

- [aalhour/C-Sharp-Algorithms on GitHub](https://github.com/aalhour/C-Sharp-Algorithms)
- [Issues](https://github.com/aalhour/C-Sharp-Algorithms/issues)
- [License: MIT](https://github.com/aalhour/C-Sharp-Algorithms/blob/master/LICENSE)
- [README](https://github.com/aalhour/C-Sharp-Algorithms/blob/master/README.md)
- [Releases](https://github.com/aalhour/C-Sharp-Algorithms/releases)

---

Hysen Labs editorial analysis, written from the project's own repository and release notes. Cite the canonical page: https://hysenlabs.com/projects/aalhour-c-sharp-algorithms