Lower bounds on approximating some variations of vertex coloring problem over restricted graph classes

Abstract

A [Formula: see text] vertex coloring of a graph [Formula: see text] partitions the vertex set into [Formula: see text] color classes (or independent sets). In minimum vertex coloring problem, the aim is to minimize the number of colors used in a given graph. Here, we consider three variations of vertex coloring problem in which (i) each vertex in [Formula: see text] dominates a color class, (ii) each color class is dominated by a vertex and (iii) each vertex is dominating a color class and each color class is dominated by a vertex. These minimization problems are known as Min-Dominator-Coloring, Min-CD-Coloring and Min-Domination-Coloring, respectively. In this paper, we present approximation hardness results for these problems for some restricted class of graphs.