Edge Coloring of Bipartite Graphs with Constraints

  • Authors:
  • Ioannis Caragiannis;Christos Kaklamanis;Pino Persiano

  • Affiliations:
  • -;-;-

  • Venue:
  • MFCS '99 Proceedings of the 24th International Symposium on Mathematical Foundations of Computer Science
  • Year:
  • 1999

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Abstract

It is a classical result from graph theory that the edges of an l-regular bipartite graph can be colored using exactly l colors so that edges that share an endpoint are assigned different colors. In this paper we study two constrained versions of the bipartite edge coloring problem. - Some of the edges adjacent to a pair of opposite vertices of an l- regular bipartite graph are already colored with S colors that appear only on one edge (single colors) and D colors that appear in two edges (double colors). We show that the rest of the edges can be colored using at most max {min{l + D, 31/2}, l + S+D/2} total colors. We also show that this bound is tight by constructing instances in which max{min{l + D, 31/2}, l + S+D/2} colors are indeed necessary. - Some of the edges of an l-regular bipartite graph are already colored with S colors that appear only on one edge. We show that the rest of the edges can be colored using at most max{l + S/2,S} total colors. We also show that this bound is tight by constructing instances in which max{l + S/2,S} total colors are necessary.