Note: On the complexity of 4-coloring graphs without long induced paths

  • Authors:
  • Van Bang Le;Bert Randerath;Ingo Schiermeyer

  • Affiliations:
  • Institut für Informatik, Universität Rostock, D-18051 Rostock, Germany;Institut für Informatik, Universität zu Köln, D-50969 Köln, Germany;Institut für Diskrete Mathematik und Algebra, TU Bergakademie Freiberg, D-09596 Freiberg, Germany

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2007

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Abstract

We show that deciding if a graph without induced paths on nine vertices can be colored with 4 colors is an NP-complete problem, improving a previous NP-completeness result proved by Woeginger and Sgall in 2001. The complexity of 4-coloring graphs without induced paths on five vertices remains open. We show that deciding if a graph without induced paths or cycles on five vertices can be colored with 4 colors can be done in polynomial time. A step in our algorithm uses the well-known and deep fact due to Grotschel, Lovasz and Schrijver stating that perfect graphs can be optimally colored in polynomial time.