Reconfiguration of List Edge-Colorings in a Graph

  • Authors:

  • Takehiro Ito;Marcin Kamiński;Erik D. Demaine

  • Affiliations:

  • Graduate School of Information Sciences, Tohoku University, Sendai, Japan 980-8579;Department of Computer Science, Université Libre de Bruxelles, Bruxelles, Belgium 1050;MIT Computer Science and Artificial Intelligence Laboratory, Cambridge, USA 02139

  • Venue:
  • WADS '09 Proceedings of the 11th International Symposium on Algorithms and Data Structures
  • Year:
  • 2009

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Abstract

We study the problem of reconfiguring one list edge-coloring of a graph into another list edge-coloring by changing one edge color at a time, while at all times maintaining a list edge-coloring, given a list of allowed colors for each edge. First we show that this problem is PSPACE-complete, even for planar graphs of maximum degree 3 and just six colors. Then we consider the problem restricted to trees. We show that any list edge-coloring can be transformed into any other under the sufficient condition that the number of allowed colors for each edge is strictly larger than the degrees of both its endpoints. This sufficient condition is best possible in some sense. Our proof yields a polynomial-time algorithm that finds a transformation between two given list edge-colorings of a tree with n vertices using O (n 2) recolor steps. This worst-case bound is tight: we give an infinite family of instances on paths that satisfy our sufficient condition and whose reconfiguration requires ***(n 2) recolor steps.