Counting and Probability
Burnside's lemma and counting under symmetry
The number of orbits under a group action equals the average number of fixed points: (1/|G|) Σ |Fix(g)|; used to count configurations up to symmetry (rotations, reflections).
0
Contest appearances
100
Practice problems
1–10
Difficulty levels
Drill this topic
Sign in and tell the coach to drill this knowledge point — it picks questions matched to your current level.