# Combinatorics Resources

## Knowledge

- [Book: _Discrete Mathematics and Its Applications_ — Kenneth Rosen](https://www.mheducation.com/highered/product/discrete-mathematics-applications-rosen/M9781260091991.html)
  Standard introductory discrete mathematics text. Use for: core counting principles, permutations, combinations, and probability-adjacent basics.
- [Open text: _Discrete Mathematics_ — Oscar Levin](https://discrete.openmathbooks.org/dmoi3.html)
  Free, well-structured introduction with combinatorics sections and exercises. Use for: beginner-friendly reading and practice.
- [MIT OpenCourseWare, Mathematics for Computer Science](https://ocw.mit.edu/courses/6-042j-mathematics-for-computer-science-spring-2015/)
  Trusted lecture notes and problem sets for foundational discrete mathematics. Use for: stronger formal follow-up once the basics feel intuitive.

## Wisdom (Communities)

- [Math StackExchange](https://math.stackexchange.com)
  Good for searching solved combinatorics questions and comparing approaches. Use for: checking reasoning after attempting a problem first.
- [Art of Problem Solving Community](https://artofproblemsolving.com/community)
  Strong problem-solving community with many combinatorics discussions. Use for: deeper challenge problems once basics are in place.

## Gaps

- Need a especially good graded progression of practice problems focused only on combinatorics.