Abstract
Given a planar straight-line graph \(G=(V,E)\) in \(\mathbb {R}^2\), a circumscribing polygon of G is a simple polygon P whose vertex set is V, and every edge in E is either an edge or an internal diagonal of P. A circumscribing polygon is a polygonization for G if every edge in E is an edge of P. We prove that every arrangement of n disjoint line segments in the plane has a subset of size \(\Omega (\sqrt{n})\) that admits a circumscribing polygon, which is the first improvement on this bound in 20 years. We explore relations between circumscribing polygons and other problems in combinatorial geometry, and generalizations to \(\mathbb {R}^3\). We show that it is NP-complete to decide whether a given graph G admits a circumscribing polygon, even if G is 2-regular. Settling a 30-year old conjecture by Rappaport, we also show that it is NP-complete to determine whether a geometric matching admits a polygonization.






















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Notes
A more accurate term would be plane straight-line graph, but we decided to use planar straight-line graph as it is a much more commonly used term in the literature.
We thank Joe Mitchell for introducing us to the high dimensional variations of this problem.
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A preliminary version of this paper appeared as research supported in part by the NSF awards CCF-1422311 and CCF-1423615. Akitaya was partially supported by NSERC.
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Akitaya, H.A., Korman, M., Korten, O. et al. Circumscribing Polygons and Polygonizations for Disjoint Line Segments. Discrete Comput Geom 68, 218–254 (2022). https://doi.org/10.1007/s00454-021-00355-8
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DOI: https://doi.org/10.1007/s00454-021-00355-8