Updating the complexity status of coloring graphs without a fixed induced linear forest

Haitze J. Broersma, P.A. Golovach, Daniël Paulusma, Jian Song

Research output: Contribution to journalArticleAcademicpeer-review

37 Citations (Scopus)

Abstract

A graph is H-free if it does not contain an induced subgraph isomorphic to the graph H. The graph Pk denotes a path on k vertices. The ℓ-Coloring problem is the problem to decide whether a graph can be colored with at most ℓ colors such that adjacent vertices receive different colors. We show that 4-Coloring is NP-complete for P8-free graphs. This improves a result of Le, Randerath, and Schiermeyer, who showed that 4-Coloring is NP-complete for P9-free graphs, and a result of Woeginger and Sgall, who showed that 5-Coloring is NP-complete for P8-free graphs. Additionally, we prove that the precoloring extension version of 4-Coloring is NP-complete for P7-free graphs, but that the precoloring extension version of 3-Coloring can be solved in polynomial time for (P2+P4)-free graphs, a subclass of P7-free graphs. Here P2+P4 denotes the disjoint union of a P2 and a P4. We denote the disjoint union of s copies of a P3 by sP3 and involve Ramsey numbers to prove that the precoloring extension version of 3-Coloring can be solved in polynomial time for sP3-free graphs for any fixed s. Combining our last two results with known results yields a complete complexity classification of (precoloring extension of) 3-Coloring for H-free graphs when H is a fixed graph on at most 6 vertices: the problem is polynomial-time solvable if H is a linear forest; otherwise it is NP-complete.
Original languageUndefined
Pages (from-to)9-19
Number of pages11
JournalTheoretical computer science
Volume414
Issue number1
DOIs
Publication statusPublished - 13 Jan 2012

Keywords

  • MSC-05C
  • Linear forest
  • EWI-21077
  • METIS-293161
  • Forbidden induced subgraph
  • Graph coloring
  • IR-82685

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