Labeling planar graphs with a condition at distance two

  • Authors:
  • Peter Bella;Daniel Král';Bojan Mohar;Katarína Quittnerová

  • Affiliations:
  • Department of Mathematical Analysis, Faculty of Mathematics and Physics, Charles University, Sokolovská 83, 186 75 Prague, Czech Republic;Department of Applied Mathematics and Institute for Theoretical Computer Science,22Institute for Theoretical Computer Science (ITI) is supported as project 1M0545 by Ministry of Education of Czech ...;Department of Mathematics, University of Ljubljana, Jadranska19, 1000 Ljubljana, Slovenia and Department of Mathematics, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada;Department of Mathematical Analysis, Faculty of Mathematics and Physics, Charles University, Sokolovská 83, 186 75 Prague, Czech Republic

  • Venue:
  • European Journal of Combinatorics
  • Year:
  • 2007

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Abstract

An L(2,1)-labeling of a graph is a mapping c:V(G)-{0,...,K} such that the labels assigned to neighboring vertices differ by at least 2 and the labels of vertices at distance two are different. The smallest K for which an L(2,1)-labeling of a graph G exists is denoted by @l"2","1(G). Griggs and Yeh [J.R. Griggs, R.K. Yeh, Labeling graphs with a condition at distance 2, SIAM J. Discrete Math. 5 (1992) 586-595] conjectured that @l"2","1(G)@?@D^2 for every graph G with maximum degree @D=2. We prove the conjecture for planar graphs with maximum degree @D3. All our results also generalize to the list-coloring setting.