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arXiv · 0711.4573

A Note On Computing Set Overlap Classes

Pierre Charbit·Michel Habib·Vincent Limouzy·Fabien De Montgolfier·Mathieu Raffinot·Michaël Rao
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Abstract

Let ${\cal V}$ be a finite set of $n$ elements and ${\cal F}=\{X_1,X_2, >..., X_m\}$ a family of $m$ subsets of ${\cal V}.$ Two sets $X_i$ and $X_j$ of ${\cal F}$ overlap if $X_i \cap X_j \neq \emptyset,$ $X_j \setminus X_i \neq \emptyset,$ and $X_i \setminus X_j \neq \emptyset.$ Two sets $X,Y\in {\cal F}$ are in the same overlap class if there is a series $X=X_1,X_2, ..., X_k=Y$ of sets of ${\cal F}$ in which each $X_iX_{i+1}$ overlaps. In this note, we focus on efficiently identifying all overlap classes in $O(n+\sum_{i=1}^m |X_i|)$ time. We thus revisit the clever algorithm of Dahlhaus of which we give a clear presentation and that we simplify to make it practical and implementable in its real worst case complexity. An useful variant of Dahlhaus's approach is also explained.

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Pierre Charbit, Michel Habib, Vincent Limouzy, Fabien De Montgolfier, Mathieu Raffinot, Michaël Rao. 2007-11-28. A Note On Computing Set Overlap Classes. https://arxiv.org/abs/0711.4573

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