For a hypergraph $\mathcal{H}=(X,\mathcal{E})$ a \emph{support} is a graph $G$ on $X$ such that for each $E\in\mathcal{E}$, the induced subgraph of $G$ on the elements in $E$ is connected. If $G$ is planar, we call it a planar support. A set of axis parallel rectangles $\mathcal{R}$ forms a non-piercing family if for any $R_1, R_2 \in \mathcal{R}$, $R_1 \setminus R_2$ is connected. Given a set $P$ of $n$ points in $\mathbb{R}^2$ and a set $\mathcal{R}$ of $m$ \emph{non-piercing} axis-aligned rectangles, we give an algorithm for computing a planar support for the hypergraph $(P,\mathcal{R})$ in $O(n\log^2 n + (n+m)\log m)$ time, where each $R\in\mathcal{R}$ defines a hyperedge consisting of all points of $P$ contained in~$R$. We use this result to show that if for a family of axis-parallel rectangles, any point in the plane is contained in at most $k$ pairwise \emph{crossing} rectangles (a pair of intersecting rectangles such that neither contains a corner of the other is called a crossing pair of rectangles), then we can obtain a support as the union of $k$ planar graphs.
翻译:对于超图 $\mathcal{H}=(X,\mathcal{E})$,其**支撑**是一个定义在 $X$ 上的图 $G$,使得对于每个 $E\in\mathcal{E}$,由 $E$ 中元素诱导的 $G$ 的子图是连通的。若 $G$ 是平面图,则称其为平面支撑。一组轴平行矩形 $\mathcal{R}$ 构成非穿透族,若对于任意 $R_1, R_2 \in \mathcal{R}$,$R_1 \setminus R_2$ 是连通的。给定 $\mathbb{R}^2$ 中一个包含 $n$ 个点的集合 $P$ 以及一组包含 $m$ 个**非穿透**轴对齐矩形的集合 $\mathcal{R}$,我们提出一种算法,可在 $O(n\log^2 n + (n+m)\log m)$ 时间内计算超图 $(P,\mathcal{R})$ 的一个平面支撑,其中每个 $R\in\mathcal{R}$ 定义了一个由 $P$ 中所有包含于 $R$ 的点构成的超边。利用这一结果,我们证明:若对于一个轴平行矩形族,平面上任意一点至多被 $k$ 个两两**交叉**的矩形所覆盖(若两个相交矩形中任一个均不包含另一个的角点,则称这对矩形为交叉矩形对),则我们可以获得一个由 $k$ 个平面图之并构成的支撑。