Combinatorics

Counting arrangements and selections.

Intermediate

$\binom{n}{k} = \frac{n!}{k!(n-k)!}$ ; precompute factorials and inverse factorials mod $p$ for fast queries. Also: inclusion-exclusion, pigeonhole, Catalan numbers.

Spotted a mistake or want to add detail? Suggest an improvement — Content Contributors' edits are reviewed by editors before they go live.

Discussion (0)