The cyclicity of a graph is the largest integer \(n\) for which the graph is contractible to the cycle on \(n\) vertices. We prove that, for \(n\) greater than three, the problem of determining whether an arbitrary graph has cyclicity \(n\) is NP-hard. We conjecture that the case \(n = 3\) is decidable in polynomial time.
Citation
Richard Hammack. A Note on the Complexity of Computing Cyclicity[J], Ars Combinatoria, Volume 063. 89-95. .