English

On Intersecting Polygons

Combinatorics 2023-03-21 v1 Computational Geometry

Abstract

Consider two regions in the plane, bounded by an nn-gon and an mm-gon, respectively. At most how many connected components can there be in their intersection? This question was asked by Croft. We answer this asymptotically, proving the bounds m2n2f(n,m)m2n2+m2\left\lfloor \frac{m}{2}\right\rfloor \cdot \left\lfloor \frac{n}{2}\right\rfloor\le f(n,m)\le \left\lfloor \frac{m}{2}\right\rfloor \cdot \frac{n}{2} + \frac{m}{2} where f(n,m)f(n,m) denotes the maximal number of components and mnm\le n. Furthermore, we give an exact answer to the related question of finding the maximal number of components if the mm-gon is required to be convex: m+n22\left \lfloor \frac{m+n-2}{2}\right\rfloor if nm+2n\ge m+2 and n2n-2 otherwise.

Keywords

Cite

@article{arxiv.2303.11208,
  title  = {On Intersecting Polygons},
  author = {Kada Williams},
  journal= {arXiv preprint arXiv:2303.11208},
  year   = {2023}
}
R2 v1 2026-06-28T09:24:26.794Z