Acyclic Edge Colouring of Outerplanar Graphs

  • Authors:
  • Rahul Muthu;N. Narayanan;C. R. Subramanian

  • Affiliations:
  • The Institute of Mathematical Sciences, Chennai, India;The Institute of Mathematical Sciences, Chennai, India;The Institute of Mathematical Sciences, Chennai, India

  • Venue:
  • AAIM '07 Proceedings of the 3rd international conference on Algorithmic Aspects in Information and Management
  • Year:
  • 2007

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Abstract

An acyclicedge colouring of a graph is a proper edge colouring having no 2-coloured cycle, that is, a colouring in which the union of any two colour classes forms a linear forest. The acyclic chromatic indexof a graph is the minimum number ksuch that there is an acyclic edge colouring using kcolours and is usually denoted by a茂戮驴(G). Determining a茂戮驴(G) exactly is a very hard problem (both theoretically and algorithmically) and is not determined even for complete graphs. We show that a茂戮驴(G) ≤ Δ(G) + 1, if Gis an outerplanar graph. This bound is tight within an additive factor of 1 from optimality. Our proof is constructive leading to an $O\!\left({n \log \Delta}\right)$ time algorithm. Here, Δ= Δ(G) denotes the maximum degree of the input graph.