On the Fine-Grained Complexity of Rainbow Coloring

Authors Lukasz Kowalik, Juho Lauri, Arkadiusz Socala

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Lukasz Kowalik
Juho Lauri
Arkadiusz Socala

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Lukasz Kowalik, Juho Lauri, and Arkadiusz Socala. On the Fine-Grained Complexity of Rainbow Coloring. In 24th Annual European Symposium on Algorithms (ESA 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 57, pp. 58:1-58:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)


The Rainbow k-Coloring problem asks whether the edges of a given graph can be colored in k colors so that every pair of vertices is connected by a rainbow path, i.e., a path with all edges of different colors. Our main result states that for any k >= 2, there is no algorithm for Rainbow k-Coloring running in time 2^{o(n^{3/2})}, unless ETH fails. Motivated by this negative result we consider two parameterized variants of the problem. In the Subset Rainbow k-Coloring problem, introduced by Chakraborty et al. [STACS 2009, J. Comb. Opt. 2009], we are additionally given a set S of pairs of vertices and we ask if there is a coloring in which all the pairs in S are connected by rainbow paths. We show that Subset Rainbow k-Coloring is FPT when parameterized by |S|. We also study Subset Rainbow k-Coloring problem, where we are additionally given an integer q and we ask if there is a coloring in which at least q anti-edges are connected by rainbow paths. We show that the problem is FPT when parameterized by q and has a kernel of size O(q) for every k >= 2, extending the result of Ananth et al. [FSTTCS 2011]. We believe that our techniques used for the lower bounds may shed some light on the complexity of the classical Edge Coloring problem, where it is a major open question if a 2^{O(n)}-time algorithm exists.
  • graph coloring
  • computational complexity
  • lower bounds
  • exponential time hypothesis
  • FPT algorithms


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