Parameterized Complexity of Geometric Covering Problems Having Conflicts

Abstract

The input for the Geometric Coverage problem consists of a pair $$\varSigma =(P,\mathcal {R})$$, where P is a set of points in $${\mathbb {R}}^d$$ and $$\mathcal {R}$$ is a set of subsets of P defined by the intersection of P with some geometric objects in $${\mathbb {R}}^d$$. Motivated by what are called choice problems in geometry, we consider a variation of the Geometric Coverage problem where there are conflicts on the covering objects that precludes some objects from being part of the solution if some others are in the solution. As our first contribution, we propose two natural models in which the conflict relations are given: (a) by a graph on the covering objects, and (b) by a representable matroid on the covering objects. Our main result is that as long as the conflict graph has bounded arboricity there is a parameterized reduction to the conflict-free version. As a consequence, we have the following results when the conflict graph has bounded arboricity. (1) If the Geometric Coverage problem is fixed parameter tractable (FPT), then so is the conflict free version. (2) If the Geometric Coverage problem admits a factor $$\alpha $$-approximation, then the conflict free version admits a factor $$\alpha $$-approximation algorithm running in FPT time. As a corollary to our main result we get a plethora of approximation algorithms that run in FPT time. Our other results include an FPT algorithm and a hardness result for conflict-free version of Covering Points by Intervals. The FPT algorithm is for the case when the conflicts are given by a representable matroid. We prove that conflict-free version of Covering Points by Intervals does not admit an FPT algorithm, unless FPT =W[1], for the family of conflict graphs for which the Independent Set problem is W[1]-hard.