In a series of papers, Avraham, Filtser, Kaplan, Katz, and Sharir (SoCG'14), Kaplan, Katz, Saban, and Sharir (ESA'23), and Katz, Saban, and Sharir (ESA'24) studied a class of geometric optimization problems - including reverse shortest path in unweighted and weighted unit-disk graphs, discrete Fréchet distance with one-sided shortcuts, and reverse shortest path in visibility graphs on 1.5-dimensional terrains - for which standard parametric search does not work well due to a lack of efficient parallel algorithms for the corresponding decision problems. The best currently known algorithms for all the above problems run in O^*(n^{6/5}) = O^*(n^{1.2}) time (ignoring subpolynomial factors), and they were obtained using a technique called shrink-and-bifurcate. We improve the running time to Õ(n^{8/7}) ≈ O(n^{1.143}) for these problems. Furthermore, specifically for reverse shortest path in unweighted unit-disk graphs, we improve the running time further to Õ(n^{9/8}) = Õ(n^{1.125}).
@InProceedings{chan_et_al:LIPIcs.SoCG.2025.32, author = {Chan, Timothy M. and Huang, Zhengcheng}, title = {{Faster Algorithms for Reverse Shortest Path in Unit-Disk Graphs and Related Geometric Optimization Problems: Improving the Shrink-And-Bifurcate Technique}}, booktitle = {41st International Symposium on Computational Geometry (SoCG 2025)}, pages = {32:1--32:14}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-370-6}, ISSN = {1868-8969}, year = {2025}, volume = {332}, editor = {Aichholzer, Oswin and Wang, Haitao}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2025.32}, URN = {urn:nbn:de:0030-drops-231845}, doi = {10.4230/LIPIcs.SoCG.2025.32}, annote = {Keywords: Geometric optimization problems, parametric search, shortest path, disk graphs, Fr\'{e}chet distance, visibility, distance selection, randomized algorithms} }
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