Enumerating all Hamilton Cycles and Bounding the Number of Hamilton Cycles in 3-Regular Graphs

Abstract

We describe an algorithm which enumerates all Hamilton cycles of a given 3-regular $n$-vertex graph in time $O(1.276^{n})$, improving on Eppstein's previous bound. The resulting new upper bound of $O(1.276^{n})$ for the maximum number of Hamilton cycles in 3-regular $n$-vertex graphs gets close to the best known lower bound of $\Omega(1.259^{n})$. Our method differs from Eppstein's in that he considers in each step a new graph and modifies it, while we fix (at the very beginning) one Hamilton cycle $C$ and then proceed around $C$, successively producing partial Hamilton cycles.