The maximum genus gamma_M(G) of a graph G is the largest genus of an orientable surface into which G has a cellular embedding. Combinatorially, it coincides with the maximum number of disjoint pairs of adjacent edges of G whose removal results in a connected spanning subgraph of G. In this paper we describe a greedy 2-approximation algorithm for maximum genus by proving that removing pairs of adjacent edges from G arbitrarily while retaining connectedness leads to at least gamma_M(G)/2 pairs of edges removed. As a consequence of our approach we also obtain a 2-approximate counterpart of Xuong's combinatorial characterisation of maximum genus.
@InProceedings{kotrbcik_et_al:OASIcs.SOSA.2019.14, author = {Kotrbc{\'\i}k, Michal and Skoviera, Martin}, title = {{Simple Greedy 2-Approximation Algorithm for the Maximum Genus of a Graph}}, booktitle = {2nd Symposium on Simplicity in Algorithms (SOSA 2019)}, pages = {14:1--14:9}, series = {Open Access Series in Informatics (OASIcs)}, ISBN = {978-3-95977-099-6}, ISSN = {2190-6807}, year = {2019}, volume = {69}, editor = {Fineman, Jeremy T. and Mitzenmacher, Michael}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.SOSA.2019.14}, URN = {urn:nbn:de:0030-drops-100409}, doi = {10.4230/OASIcs.SOSA.2019.14}, annote = {Keywords: maximum genus, embedding, graph, greedy algorithm} }
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