The maximum independent set problem seeks a maximum independent vertex set in a given graph. The optimal
size is its independence number. The optimization
problem is NP-hard. Its decision version asks
whether the independence number is at least
a given integer and is NP-complete
(Garey and Johnson 1983).
Song (2026) gave a deterministic approximation algorithm for an -vertex
graph with approximation ratio
and running time
. The guarantee uses quasipolynomial
time.