Abstract
We investigate the computational complexity of the Densest- k -Subgraph (D k S) problem, where the input is an undirected graph G = (V,E) and one wants to find a subgraph on exactly k vertices with a maximum number of edges. We extend previous work on D k S by studying its parameterized complexity. On the positive side, we show that, when fixing some constant minimum density μ of the sought subgraph, D k S becomes fixed-parameter tractable with respect to either of the parameters maximum degree and h-index of G. Furthermore, we obtain a fixed-parameter algorithm for D k S with respect to the combined parameter “degeneracy of G and |V| − k”. On the negative side, we find that D k S is W[1]-hard with respect to the combined parameter “solution size k and degeneracy of G”. We furthermore strengthen a previous hardness result for D k S [Cai, Comput. J., 2008] by showing that for every fixed μ, 0 < μ < 1, the problem of deciding whether G contains a subgraph of density at least μ is W[1]-hard with respect to the parameter |V| − k.
One result of this work (Thm. 4) is contained in the first author’s dissertation [16].
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Komusiewicz, C., Sorge, M. (2012). Finding Dense Subgraphs of Sparse Graphs. In: Thilikos, D.M., Woeginger, G.J. (eds) Parameterized and Exact Computation. IPEC 2012. Lecture Notes in Computer Science, vol 7535. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-33293-7_23
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DOI: https://doi.org/10.1007/978-3-642-33293-7_23
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