English

Coloring directed cycles

Discrete Mathematics 2013-07-22 v1 Combinatorics

Abstract

Sopena in his survey [E. Sopena, The oriented chromatic number of graphs: A short survey, preprint 2013] writes, without any proof, that an oriented cycle C\vec C can be colored with three colors if and only if λ(C)=0\lambda(\vec C)=0, where λ(C)\lambda(\vec C) is the number of forward arcs minus the number of backward arcs in C\vec C. This is not true. In this paper we show that C\vec C can be colored with three colors if and only if λ(C)=0(mod 3)\lambda(\vec C)=0(\bmod~3) or C\vec C does not contain three consecutive arcs going in the same direction.

Cite

@article{arxiv.1307.5186,
  title  = {Coloring directed cycles},
  author = {Andrzej Szepietowski},
  journal= {arXiv preprint arXiv:1307.5186},
  year   = {2013}
}
R2 v1 2026-06-22T00:54:16.247Z