Computing L(p, 1)-Labeling with Combined Parameters

Tesshu Hanaka, Kazuma Kawai, Hirotaka Ono

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


Given a graph, an L(p, 1)-labeling of the graph is an assignment f from the vertex set to the set of nonnegative integers such that for any pair of vertices u and v, |f(u) − f(v)| ≥ p if u and v are adjacent, and f(u) ≠ f(v) if u and v are at distance 2. The L(p, 1)-labeling problem is to minimize the span of f (i.e.,maxu∈V (f(u)) − minu∈V (f(u)) + 1). It is known to be NP-hard even for graphs of maximum degree 3 or graphs with tree-width 2, whereas it is fixed-parameter tractable with respect to vertex cover number. Since the vertex cover number is a kind of the strongest parameter, there is a large gap between tractability and intractability from the viewpoint of parameterization. To fill up the gap, in this paper, we propose new fixed-parameter algorithms for L(p, 1)-Labeling by the twin cover number plus the maximum clique size and by the tree-width plus the maximum degree. These algorithms reduce the gap in terms of several combinations of parameters.

Original languageEnglish
Pages (from-to)241-255
Number of pages15
JournalJournal of Graph Algorithms and Applications
Issue number2
Publication statusPublished - 2022
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Theoretical Computer Science
  • General Computer Science
  • Computer Science Applications
  • Geometry and Topology
  • Computational Theory and Mathematics


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