Abstract
We explore an extension to rectilinear convexity of the classic problem of computing the convex hull of a collection of line segments. Namely, we solve the problem of computing and maintaining the rectilinear convex hull of a set of n line segments, while we simultaneously rotate the coordinate axes by an angle that goes from 0 to \(2\pi \).
We describe an algorithm that runs in optimal \(\varTheta (n\log n)\) time and \(\varTheta (n\alpha (n))\) space for segments that are non-necessarily disjoint, where \(\alpha (n)\) is the inverse of the Ackermann’s function. If instead the line segments form a simple polygonal chain, the algorithm can be adapted so as to improve the time and space complexities to \(\varTheta (n)\).
Keywords
- rectilinear convex hull
- line segments
- polygonal lines
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See the definition of the maximal r-convex hull in [15].
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We remark that, since the set \(\mathcal {O}\) is formed by two orthogonal lines parallel to the coordinate axis, in this paper \(\mathcal {O}\)-convexity is equivalent to Orthogonal Convexity.
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Acknowledgements
Justin Dallant is supported by the French Community of Belgium via the funding of a FRIA grant. Pablo Pérez-Lantero was partially supported by project DICYT 042332PL Vicerrectoría de Investigación, Desarrollo e Innovación USACH (Chile). Carlos Seara is supported by Project PID2019-104129GB-I00/AEI/10.13039/501100011033 of the Spanish Ministry of Science and Innovation.
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Alegría, C., Dallant, J., Pérez-Lantero, P., Seara, C. (2023). The Rectilinear Convex Hull of Line Segments. In: Fernau, H., Jansen, K. (eds) Fundamentals of Computation Theory. FCT 2023. Lecture Notes in Computer Science, vol 14292. Springer, Cham. https://doi.org/10.1007/978-3-031-43587-4_3
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