Approximation schemes for independent set and sparse subsets of polygons

Research output: Contribution to journalJournal articleResearchpeer-review

  • Anna Adamaszek
  • Sariel Har-Peled
  • Andreas Wiese

We present a (1 + ε)-approximation algorithm with quasi-polynomial running time for computing a maximum weight independent set of polygons from a given set of polygons in the plane. Contrasting this, the best-known polynomial time algorithm for the problem has an approximation ratio of nε. Surprisingly, we can extend the algorithm to the problem of computing the maximum cardinality subset of the given set of polygons whose intersection graph fulfills some sparsity condition. For example, we show that one can approximate the maximum subset of polygons such that the intersection graph of the subset is planar or does not contain a cycle of length 4 (i.e., K2,2). Our algorithm relies on a recursive partitioning scheme, whose backbone is the existence of balanced cuts with small complexity that intersect polygons from the optimal solution of a small total weight. For the case of large axis-parallel rectangles, we provide a polynomial time (1 + ε)-approximation for the maximum weight independent set. Specifically, we consider the problem where each rectangle has one edge whose length is at least a constant fraction of the length of the corresponding edge of the bounding box of all the input elements. This is now the most general case for which a PTAS is known, and it requires a new and involved partitioning scheme, which should be of independent interest.

Original languageEnglish
Article number29
JournalJournal of the ACM
Volume66
Issue number4
Number of pages40
ISSN0004-5411
DOIs
Publication statusPublished - 2019

    Research areas

  • Approximation algorithms, Approximation schemes, Independent set, Rectangles

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