Polyominoes with maximal number of deep holes
Djordje Baralic, Shiven Uppal
TL;DR
The paper addresses the problem of determining the maximal number of deep holes that can be enclosed by an $n$-omino, denoted $h_n$. It combines constructive lower-bound techniques with a generalized Pick's theorem-based upper bound to establish $h_n = \frac{n}{3} + o(n)$ asymptotically, and computes $h_n$ exactly for an infinite subset of $n$ via detailed constructions and case analysis. The key contributions are tight asymptotic results, explicit lower bounds, and exact values for families of $n$, along with a framework that yields precise upper bounds. This advances understanding of deep-hole capacity in lattice-based polyominoes and informs related tiling/topology problems on planar grids.
Abstract
In this paper, we study the extremal behaviour of deep holes in polyominoes. We determine the maximum number, $h_n$ of deep holes that an $n$-omino can enclose, ensuring that the boundary of each hole is disjoint from the boundaries of any other hole and from the outer boundary of the $n$-tile. Using the versatile application of Pick's theorem, we establish the lower and the upper bound for $h_n$, and show that $h_n=\frac{n}{3}+o(n)$ asymptotically. To further develop these results, we compute $h_n$ as a function of $n$ for an infinite subset of positive integers.
