Coloring graphs without short cycles and long induced paths

  • Authors:
  • Petr A. Golovach;Daniël Paulusma;Jian Song

  • Affiliations:
  • -;-;-

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2014

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Abstract

For an integer k=1, a graph G is k-colorable if there exists a mapping c:V"G-{1,...,k} such that c(u)c(v) whenever u and v are two adjacent vertices. For a fixed integer k=1, the k-Coloring problem is that of testing whether a given graph is k-colorable. The girth of a graph G is the length of a shortest cycle in G. For any fixed g=4 we determine a lower bound @?(g), such that every graph with girth at least g and with no induced path on @?(g) vertices is 3-colorable. We also show that for all fixed integers k,@?=1, thek-Coloring problem can be solved in polynomial time for graphs with no induced cycle on four vertices and no induced path on @? vertices. As a consequence, for all fixed integers k,@?=1 and g=5, the k-Coloring problem can be solved in polynomial time for graphs with girth at least g and with no induced path on @? vertices. This result is best possible, as we prove the existence of an integer @?^*, such that already 4-Coloring is NP-complete for graphs with girth 4 and with no induced path on @?^* vertices.