Distance constrained labelings of trees

  • Authors:
  • Jiří Fiala;Petr A. Golovach;Jan Kratochvíl

  • Affiliations:
  • Institute for Theoretical Computer Science and Department of Applied Mathematics, Charles University, Prague, Czech Republic;Institutt for informatikk, Universitetet i Bergen, Norway;Institute for Theoretical Computer Science and Department of Applied Mathematics, Charles University, Prague, Czech Republic

  • Venue:
  • TAMC'08 Proceedings of the 5th international conference on Theory and applications of models of computation
  • Year:
  • 2008

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Abstract

An H(p, q)-labeling of a graph G is a vertex mapping f : VG → VH such that the distance between f(u) and f(v) (measured in the graph H) is at least p if the vertices u and v are adjacent in G, and the distance is at least q if u and v are at distance two in G. This notion generalizes the notions of L(p, q)- and C(p, q)-labelings of graphs studied as particular graph models of the Frequency Assignment Problem. We study the computational complexity of the problem of deciding the existence of such a labeling when the graphs G and H come from restricted graph classes. In this way we extend known results for linear and cyclic labelings of trees, with a hope that our results would help to open a new angle of view on the still open problem of L(p, q)-labeling of trees for fixed p q 1 (i.e., when G is a tree and H is a path). We present a polynomial time algorithm for H(p, 1)-labeling of trees for arbitrary H. We show that the H(p, q)-labeling problem is NP-complete when the graph G is a star. As the main result we prove NP-completeness for H(p, q)-labeling of trees when H is a symmetric q-caterpillar.