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Equitable colorings of l-corona products of cubic graphs

Furmańczyk Hanna, Kubale Marek

Archives of Control Sciences

2024

Vol. 34, No. 1

211--223

A graph 𝐺 is equitably 𝑘-colorable if its vertices can be partitioned into k independent sets in such a way that the number of vertices in any two sets differ by at most one. The smallest integer 𝑘 for which such a coloring exists is known as the equitable chromatic number of 𝐺 and it is denoted by x=(𝐺). In this paper the problem of determining the value of equitable chromatic number for multicoronas of cubic graphs G ◦l H is studied. The problem of ordinary coloring of multicoronas of cubic graphs is solvable in polynomial time. The complexity of equitable coloring problem is an open question for these graphs. We provide some polynomially solvable cases of cubical multicoronas and give simple linear time algorithms for equitable coloring of such graphs which use at most x=(G ◦l H) + 1 colors in the remaining cases.

Better polynomial algorithms for scheduling unit-length jobswith bipartite incompatibility graphs on uniform machines

Pikies T., Kubale Marek

Bulletin of the Polish Academy of Sciences. Technical Sciences

2019

Vol. 67, nr 1

31--36

The goal of this paper is to explore and to provide tools for the investigation of the problems of unit-length scheduling of incompatible jobs on uniform machines. We present two new algorithms that are a significant improvement over the known algorithms. The first one is Algorithm 2 which is 2-approximate for the problem Qm|pj = 1, G = bisubquartic|Cmax. The second one is Algorithm 3 which is 4-approximate for the problem Qm|pj = 1, G = bisubquartic|ΣCj, where m ϵ {2, 3, 4}. The theory behind the proposed algorithms is based on the properties of 2-coloring with maximal coloring width, and on the properties of ideal machine, an abstract machine that we introduce in this paper.