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Let c, k be two positive integers. Given a graph G=(V,E), the c-Load Coloring problem asks whether there is a c-coloring varphi: V => [c] such that for every i in [c], there are at least k edges with both endvertices colored i. Gutin and Jones (IPL 2014) studied this problem with c=2. They showed 2-Load Coloring to be fixed-parameter tractable (FPT) with parameter k by obtaining a kernel with at most 7k vertices. In this paper, we extend the study to any fixed c by giving both a linear-vertex and a linear-edge kernel. In the particular case of c=2, we obtain a kernel with less than 4k vertices and less than 8k edges. These results imply that for any fixed c >= 2, c-Load Coloring is FPT and the optimization version of c-Load Coloring (where k is to be maximized) has an approximation algorithm with a constant ratio.
@InProceedings{barbero_et_al:LIPIcs.IPEC.2015.43,
author = {Barbero, Florian and Gutin, Gregory and Jones, Mark and Sheng, Bin},
title = {{Parameterized and Approximation Algorithms for the Load Coloring Problem}},
booktitle = {10th International Symposium on Parameterized and Exact Computation (IPEC 2015)},
pages = {43--54},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-939897-92-7},
ISSN = {1868-8969},
year = {2015},
volume = {43},
editor = {Husfeldt, Thore and Kanj, Iyad},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2015.43},
URN = {urn:nbn:de:0030-drops-55703},
doi = {10.4230/LIPIcs.IPEC.2015.43},
annote = {Keywords: Load Coloring, fixed-parameter tractability, kernelization}
}