Fast exact algorithm for L(2, 1)-labeling of graphs

  • Authors:
  • Konstanty Junosza-Szaniawski;Jan Kratochvíl;Mathieu Liedloff;Peter Rossmanith;Paweł Rzazewski

  • Affiliations:
  • Warsaw University of Technology, Faculty of Mathematics and Information Science, Warszawa, Poland;Department of Applied Mathematics, and Institute for Theoretical Computer Science, Charles University,Praha, Czech Republic;Laboratoire d'Informatique Fondamentale d'Orléans, Université d'Orléans, Orléans Cedex, France;Department of Computer Science, RWTH Aachen University, Germany;Warsaw University of Technology, Faculty of Mathematics and Information Science, Warszawa, Poland

  • Venue:
  • TAMC'11 Proceedings of the 8th annual conference on Theory and applications of models of computation
  • Year:
  • 2011

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Abstract

An L(2, 1)-labeling of a graph is a mapping from its vertex set into nonnegative integers such that the labels assigned to adjacent vertices differ by at least 2, and labels assigned to vertices of distance 2 are different. The span of such a labeling is the maximum label used, and the L(2, 1)-span of a graph is the minimum possible span of its L(2, 1)- labelings. We show how to compute the L(2, 1)-span of a connected graph in time O*(2.6488n). Previously published exact exponential time algorithms were gradually improving the base of the exponential function from 4 to the so far best known 3.2361, with 3 seemingly having been the Holy Grail.