,
Ahmad Biniaz,
Erik D. Demaine
,
Linda Kleist
,
Frederick Stock,
Csaba D. Tóth
Creative Commons Attribution 4.0 International license
For a set of red and blue points in the plane, a minimum bichromatic spanning tree (MinBST) is a shortest spanning tree of the points such that every edge has a red and a blue endpoint. A MinBST can be computed in O(n log n) time where n is the number of points. In contrast to the standard Euclidean MST, which is always plane (noncrossing), a MinBST may have edges that cross each other. However, we prove that a MinBST is quasi-plane, that is, it does not contain three pairwise crossing edges, and we determine the maximum number of crossings. Moreover, we study the problem of finding a minimum plane bichromatic spanning tree (MinPBST) which is a shortest bichromatic spanning tree with pairwise noncrossing edges. This problem is known to be NP-hard. The previous best approximation algorithm, due to Borgelt et al. (2009), has a ratio of O(√n). It is also known that the optimum solution can be computed in polynomial time in some special cases, for instance, when the points are in convex position, collinear, semi-collinear, or when one color class has constant size. We present an O(log n)-factor approximation algorithm for the general case.
@InProceedings{a.akitaya_et_al:LIPIcs.ISAAC.2024.4,
author = {A. Akitaya, Hugo and Biniaz, Ahmad and Demaine, Erik D. and Kleist, Linda and Stock, Frederick and T\'{o}th, Csaba D.},
title = {{Minimum Plane Bichromatic Spanning Trees}},
booktitle = {35th International Symposium on Algorithms and Computation (ISAAC 2024)},
pages = {4:1--4:14},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-354-6},
ISSN = {1868-8969},
year = {2024},
volume = {322},
editor = {Mestre, Juli\'{a}n and Wirth, Anthony},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2024.4},
URN = {urn:nbn:de:0030-drops-221319},
doi = {10.4230/LIPIcs.ISAAC.2024.4},
annote = {Keywords: Bichromatic Spanning Tree, Minimum Spanning Tree, Plane Tree}
}