Rainbow and strong rainbow connection number for some families of graphs

Abstract

Let G be a nontrivial connected graph. Then G is called a rainbow connected graph if there exists a coloring c : E(G) → {1, 2, ..., k}, k ∈ N, of the edges of G, such that there is a u − v rainbow path between every two vertices of G, where a path P in G is a rainbow path if no two edges of P are colored the same. The minimum k for which there exists such a k-edge coloring is the rainbow connection number rc(G) of G. If for every pair u, v of distinct vertices, G contains a rainbow u − v geodesic, then G is called strong rainbow connected. The minimum k for which G is strong rainbow-connected is called the strong rainbow connection number src(G) of G. The exact rc and src of the rotationally symmetric graphs are determined.