Non-crossing connectors in the plane
J Kratochvíl, T Ueckerdt - Theory and Applications of Models of …, 2013 - Springer
Theory and Applications of Models of Computation: 10th International …, 2013•Springer
We consider the non-crossing connectors problem, which is stated as follows: Given n
regions R 1,…, R n in the plane and finite point sets P i⊂ R i for i= 1,…, n, are there non-
crossing connectors γ i for (R i, P i), ie, arc-connected sets γ i with P i⊂ γ i⊂ R i for every i=
1,…, n, such that γ i∩ γ j=∅ for all i≠ j? We prove that non-crossing connectors do always
exist if the regions form a collection of pseudo-disks, ie, the boundaries of every pair of
regions intersect at most twice. We provide a simple polynomial-time algorithm if each …
regions R 1,…, R n in the plane and finite point sets P i⊂ R i for i= 1,…, n, are there non-
crossing connectors γ i for (R i, P i), ie, arc-connected sets γ i with P i⊂ γ i⊂ R i for every i=
1,…, n, such that γ i∩ γ j=∅ for all i≠ j? We prove that non-crossing connectors do always
exist if the regions form a collection of pseudo-disks, ie, the boundaries of every pair of
regions intersect at most twice. We provide a simple polynomial-time algorithm if each …
Abstract
We consider the non-crossing connectors problem, which is stated as follows: Given n regions R 1,…,R n in the plane and finite point sets P i ⊂ R i for i = 1,…,n, are there non-crossing connectors γ i for (R i ,P i ), i.e., arc-connected sets γ i with P i ⊂ γ i ⊂ R i for every i = 1,…,n, such that γ i ∩ γ j = ∅ for all i ≠ j?
We prove that non-crossing connectors do always exist if the regions form a collection of pseudo-disks, i.e., the boundaries of every pair of regions intersect at most twice. We provide a simple polynomial-time algorithm if each region is the convex hull of the corresponding point set, or if all regions are axis-aligned rectangles. We prove that the general problem is NP-hard, even if the regions are convex, the boundaries of every pair of regions intersect at most four times and P i consists of only two points on the boundary of R i for i = 1,…,n.
Finally, we prove that the non-crossing connectors problem lies in NP, i.e., is NP-complete, by a reduction to a non-trivial problem, and that there indeed are problem instances in which every solution has exponential complexity, even when all regions are convex pseudo-disks.
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