Problem Forge
Problem Forge has no forum of its own. These are places where people talk about this kind of problem. Each has its own rules; read them before you post. Some ban posts written by AI, and some ask you to say when you used it. Places marked (Discord) are chat servers on Discord; you need a Discord account to read them.
Algorithms and theory
- Computer Science Stack Exchange: algorithms and hard problems.
- Theoretical Computer Science Stack Exchange: research-level questions on complexity and algorithms.
- r/algorithms: designing algorithms.
- r/AskComputerScience: questions about computer science. Beginners are welcome.
- r/compsci: computer science articles and discussion; not for homework help.
Solvers and optimisation
- Operations Research Stack Exchange: optimisation, solvers and the travelling salesperson problem.
- r/OperationsResearch: optimisation and routing.
- OR-Tools discussion group: Google's free solver suite, including CP-SAT.
- MiniZinc discussion group: a language for writing constraint models and running them on many solvers.
- HiGHS discussions: a free solver for linear and integer programs.
- Z3 discussions: Microsoft's free logic solver, which handles SAT and more.
- Gurobi Community: a commercial optimisation solver; modelling and algorithm questions.
- Kaggle Santa competitions: an optimisation contest each December, with a busy discussion board (this link is the 2025 contest).
- Kaggle (Discord): Kaggle's server, with channels for its competitions.
- Google OR-Tools (Discord): chat about OR-Tools and CP-SAT, linked from Google's support page.
AI and LLMs
- r/ChatGPTCoding: coding with AI tools of every kind, not only ChatGPT.
- r/ClaudeAI: using Claude; not run by Anthropic.
- r/ClaudeCode: using Claude Code, an AI coding agent.
- r/OpenAI: OpenAI's models and tools, including Codex; not run by OpenAI.
- r/cursor: the Cursor AI code editor.
- r/GithubCopilot: GitHub Copilot; not run by GitHub.
- r/LocalLLaMA: running AI models on your own computer.
- r/LLMDevs: building programs that use language models.
- r/MachineLearning: machine learning research; beginner questions go elsewhere.
- Hugging Face Forums: open AI models and tools; has a beginners section.
- OpenAI Developer Community: building with OpenAI's API and Codex.
- Claude (Discord): Anthropic's server for Claude and Claude Code.
- OpenAI (Discord): OpenAI's server for ChatGPT, Codex and its models.
- Hugging Face (Discord): open AI models and tools.
- Google Developer Community (Discord): Google's developer server; Gemini has its own channels.
- DeepSeek (Discord): the DeepSeek models.
- Ollama (Discord): running open models on your own computer with Ollama.
Programming
- Stack Overflow: questions about specific code.
- Code Review Stack Exchange: ask others to review working code.
- r/learnprogramming: programming questions in any language; beginners welcome.
- r/programming: programming articles and news; AI tools are mostly off-topic.
- r/cpp: the C++ language.
- r/C_Programming: the C language.
- r/rust: the Rust language.
- Together C & C++ (Discord): help and discussion on C and C++.
- Rust Community (Discord): learning and using Rust; not run by the Rust project.
- Python (Discord): the Python language; beginners welcome.
- Hacker News: links and discussion on programming and technology.
- Lobsters: links and discussion on programming; joining needs an invitation.
Contests and puzzles
- r/adventofcode: the forum of Advent of Code, a yearly puzzle event. Most posts are about Advent of Code.
- r/everybodycodes: forum of Everybody Codes, a yearly puzzle event like Advent of Code.
- Codeforces: programming contests, with blogs where people discuss problems.
- USACO Guide (Discord): the server of the USACO Guide's authors, for competitive programming.
- CodinGame (Discord): puzzles, bot contests and quick "clash" rounds on CodinGame.
- Project Euler: math and programming problems; each problem has a discussion thread that opens once you solve it.
- Code Golf Stack Exchange: contests for the shortest or fastest program.
- Puzzling Stack Exchange: logic puzzles and how to solve them.
- r/puzzles: sharing and solving puzzles of all kinds.
- r/dailyprogrammer: an archive of several hundred programming challenges with their discussions; no longer updated.
Mathematics
- Mathematics Stack Exchange: graphs, sums and counting, at any level.
- MathOverflow: research-level math only.
- r/math: discussion of mathematics; simple questions go in its weekly thread.
- r/askmath: math questions at any level.
- Mathematics (Discord): learning and discussing mathematics, from school level to research.