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LeetCode in C++

A collection of LeetCode solutions written entirely in C++23. Every solved problem ships with an automated unit test, and the same problem is often solved from more than one angle — brute force, optimized, recursive, and so on — living side by side in the same files, with build, static analysis, and format checks running on every pull request.

Why multiple approaches per problem

Solving a problem once proves you found an answer. Solving it again as a brute-force baseline, again as the optimized version, again recursively (or however else it can be attacked) proves you understand why the answer works — and leaves a reference for how the same idea looks under different constraints. It isn't a requirement for every problem, but the structure is ready for it whenever it's worth doing.

Repository structure

solutions/
  0001-0100/
    0001-two-sum/
      README.md         # problem statement summary, link, difficulty, tags
      solution.hpp       # public interface — one function per approach
      solution.cpp       # implementation
      test.cpp           # Catch2 tests — one TEST_CASE per approach
  0101-0200/
    ...

Problems are grouped in ranges of 100 so the repository stays easy to browse well past problem #3000. Every problem is a single folder with exactly three code files — never a folder per approach: when a problem is solved more than one way, each approach is a separate function (or method) in the same solution.hpp/solution.cpp, tested by its own TEST_CASE in the same test.cpp. The problem's README.md documents the problem itself (statement summary, link, difficulty, tags), not the approaches, which are documented as comments in the code.

Every problem must ship a test — a solution without a test.cpp covering it isn't considered done.

SQL problems have no meaningful C++ equivalent (LeetCode expects a SQL query, not a program), so the legacy sql/ folder is kept as-is and out of scope for this migration.

Commit convention

Every commit is tagged with an emoji describing its intent:

Emoji	Meaning
🟢	Solves an easy problem
🟡	Solves a medium problem
🔴	Solves a hard problem
🐛	Bug fix
📝	Documentation update
🚀	Performance improvement
⚡️	Refactor
🎨	Formatting / structural style
🚧	Work in progress
🔧	Tooling, build system, or CI change

Building and testing locally

Requirements: CMake ≥ 3.20 and a C++23 compiler (GCC ≥ 13 or Clang ≥ 16).

cmake -S . -B build
cmake --build build --parallel
ctest --test-dir build --output-on-failure

Continuous integration

Every pull request runs three checks:

1. Build & test — CMake + Catch2 against every problem's test.cpp.
2. Static analysis — clang-tidy and cppcheck.
3. Format check — clang-format --dry-run --Werror.

Progress

🚧 This repository is being migrated to C++23. Existing solutions previously written in other languages (Clojure, Go, Python, Ruby, Swift, TypeScript) are being converted one pull request at a time.

Contributing

See CONTRIBUTING.md for the folder convention, commit style, and how to add a new problem.

License

MIT — see LICENSE.