On Equitable Coloring of d-Degenerate Graphs

  • Authors:
  • A. V. Kostochka;K. Nakprasit;S. V. Pemmaraju

  • Affiliations:
  • -;-;-

  • Venue:
  • SIAM Journal on Discrete Mathematics
  • Year:
  • 2005

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Abstract

An equitable coloring of a graph is a proper vertex coloring such that the sizes of any two color classes differ by at most 1. A d-degenerate graph is a graph G in which every subgraph has a vertex with degree at most d. A star Sm with m rays is an example of a 1-degenerate graph with maximum degree m that needs at least 1+m/2 colors for an equitable coloring. Our main result is that every n-vertex d-degenerate graph G with maximum degree at most n/15 can be equitably k-colored for each $k \ge 16d$. The proof of this bound is constructive. We extend the algorithm implied in the proof to an O(d)-factor approximation algorithm for equitable coloring of an arbitrary d-degenerate graph. Among the implications of this result is an O(1)-factor approximation algorithm for equitable coloring of planar graphs with fewest colors. A variation of equitable coloring (equitable partitions) is also discussed.