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On the shortest separating cycle
Computational Geometry ( IF 0.6 ) Pub Date : 2020-01-31 , DOI: 10.1016/j.comgeo.2020.101612
Adrian Dumitrescu

According to a result of Arkin et al. (2016), given n point pairs in the plane, there exists a simple polygonal cycle that separates the two points in each pair to different sides; moreover, a O(n)-factor approximation with respect to the minimum length can be computed in polynomial time. Here the following results are obtained:

(I) We extend the problem to geometric hypergraphs and obtain the following characterization of feasibility. Given a geometric hypergraph on points in the plane with hyperedges of size at least 2, there exists a simple polygonal cycle that separates each hyperedge if and only if the hypergraph is 2-colorable.

(II) We extend the O(n)-factor approximation in the length measure as follows: Given a geometric graph G=(V,E), a separating cycle (if it exists) can be computed in O(m+nlogn) time, where |V|=n, |E|=m. Moreover, a O(n)-approximation of the shortest separating cycle can be found in polynomial time. Given a geometric graph G=(V,E) in R3, a separating polyhedron (if it exists) can be found in O(m+nlogn) time, where |V|=n, |E|=m. Moreover, a O(n2/3)-approximation of a separating polyhedron of minimum perimeter can be found in polynomial time.

(III) Given a set of n point pairs in convex position in the plane, we show that a (1+ε)-approximation of a shortest separating cycle can be computed in time nO(ε1/2). In this regard, we prove a lemma on convex polygon approximation that is of independent interest.



中文翻译:

在最短的分离周期内

根据Arkin等人的结果。(2016年),给定平面中的n个点对,存在一个简单的多边形循环,将每对中的两个点分隔到不同的侧面;而且,一个Øñ可以在多项式时间内计算出与最小长度相关的系数近似值。在这里获得以下结果:

(I)将问题扩展到几何超图,并获得以下可行性描述。给定在平面上具有至少2个超边的点的几何超图,则存在一个简单的多边形循环,当且仅当超图是2色的时,才将每个超边分开。

(II)我们扩展 Øñ长度度量中的系​​数近似,如下所示:给定几何图 G=VË,可以计算出一个分离周期(如果存在) Ø+ñ日志ñ 时间,地点 |V|=ñ|Ë|=。此外,Øñ-最短分离周期的近似值可以在多项式时间内找到。给定几何图G=VË[R3,可以在以下位置找到一个分离的多面体(如果存在) Ø+ñ日志ñ 时间,地点 |V|=ñ|Ë|=。此外,Øñ2/3最小周长的分离多面体的近似值可以在多项式时间内找到。

(III)给定一组n个点对在平面上的凸位置,我们证明1个+ε-最短分离周期的近似值可以及时计算 ñØε-1个/2。在这方面,我们证明了凸多边形逼近中的一个引人注目的引理。

更新日期:2020-01-31
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