Optimal L(d,1)-labelings of certain direct products of cycles and Cartesian products of cycles

  • Authors:
  • Pranava K. Jha;Sandi Klavžar;Aleksander Vesel

  • Affiliations:
  • Department of Computer Science, St. Cloud State University, St. Cloud, MN;Department of Mathematics and Computer Science, University of Maribor, Maribor, Slovenia;Department of Mathematics and Computer Science, University of Maribor, Maribor, Slovenia

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2005

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Abstract

An L(d,1)-labeling of a graph G is an assignment of nonnegative integers to the vertices such that adjacent vertices receive labels that differ by at least d and those at a distance of two receive labels that differ by at least one, where d ≥ 1. Let λ1d(G) denote the least λ such that G admits an L(d,1)-labeling using labels from {0, 1, ..., λ}. We prove that (i) if d ≥ 1, k ≥ 2 and m0, ..., mk-1 are each a multiple of 2k + 2d - 1, then λ1d(Cm0 × ... × Cmk-1) ≤ 2k + 2d - 2, with equality if 1 ≤ d ≤ 2k, and (ii) if d ≥ 1, k ≥ 1 and m0, ..., mk-1 are each a multiple of 2k + 2d - 1, then λ1d (Cm0□ ...□Cmk-1) ≤ 2k + 2d - 2, with equality if 1 ≤ d ≤ 2k.