An FPT-algorithm for recognizing k-apices of minor-closed graph classes

04/27/2020

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by   Ignasi Sau, et al.

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Let G be a graph class. We say that a graph G is a k-apex of G if G contains a set S of at most k vertices such that G∖ S belongs to G. We prove that if G is minor-closed, then there is an algorithm that either returns a set S certifying that G is a k-apex of G or reports that such a set does not exist, in 2^ poly(k)· n^3 time. Here poly is a polynomial function whose degree depends on the maximum size of a minor-obstruction of G, i.e., the minor-minimal set of graphs not belonging to G. In the special case where G excludes some apex graph as a minor, we give an alternative algorithm running in 2^ poly(k)· n^2 time.