On rainbow connection

Yair Caro, Arie Lev, Yehuda Roditty, Zsolt Tuza, Raphael Yuster

Research output: Contribution to journalArticlepeer-review


An edge-colored graph G is rainbow connected if any two vertices are connected by a path whose edges have distinct colors. The rainbow connection number of a connected graph G, denoted rc(G), is the smallest number of colors that are needed in order to make G rainbow connected. In this paper we prove several non-trivial upper bounds for rc(G), as well as determine sufficient conditions that guarantee rc(G) = 2. Among our results we prove that if G is a connected graph with n vertices and with minimum degree 3 then rc(G) < 5n/6, and if the minimum degree is 6 then rc(G) ≤ lnδ/δn(1 + o δ(1)). We also determine the threshold function for a random graph to have rc(G) = 2 and make several conjectures concerning the computational complexity of rainbow connection.

Original languageEnglish
Article numberR57
JournalElectronic Journal of Combinatorics
Issue number1 R
StatePublished - 18 Apr 2008

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Geometry and Topology
  • Discrete Mathematics and Combinatorics
  • Computational Theory and Mathematics
  • Applied Mathematics


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