Neighbor-locating coloring: graph operations and extremal cardinalities

Abstract A k–coloring of a graph G = ( V , E ) is a k-partition Π = { S 1 , … , S k } of V into independent sets, called colors. A k-coloring is called neighbor-locating if for every pair of vertices u, v belonging to the same color S i , the set of colors of the neighborhood of u is different from the set of colors of the neighborhood of v. The neighbor-locating chromatic number, χ NL ( G ) , is the minimum cardinality of a neighbor-locating coloring of G. In this paper, we examine the neighbor-locating chromatic number for various graph operations: the join, the disjoint union and Cartesian product. We also characterize all connected graphs of order n ≥ 3 with neighbor-locating chromatic number equal either to n or to n − 1 and determine the neighbor-locating chromatic number of split graphs.