We study the problem of computing the diameter and the mean distance of a continuous graph, i.e., a connected graph where all points along the edges, instead of only the vertices, must be taken into account. It is known that for continuous graphs with m edges these values can be computed in roughly O(m²) time. In this paper, we use geometric techniques to obtain subquadratic time algorithms to compute the diameter and the mean distance of a continuous graph for two well-established classes of sparse graphs. We show that the diameter and the mean distance of a continuous graph of treewidth at most k can be computed in O(n log^O(k) n) time, where n is the number of vertices in the graph. We also show that computing the diameter and mean distance of a continuous planar graph with n vertices and F faces takes O(n F log n) time.
@InProceedings{cabello_et_al:LIPIcs.WADS.2025.13, author = {Cabello, Sergio and Garijo, Delia and Kalb, Antonia and Klute, Fabian and Parada, Irene and Silveira, Rodrigo I.}, title = {{Algorithms for Distance Problems in Continuous Graphs}}, booktitle = {19th International Symposium on Algorithms and Data Structures (WADS 2025)}, pages = {13:1--13:14}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-398-0}, ISSN = {1868-8969}, year = {2025}, volume = {349}, editor = {Morin, Pat and Oh, Eunjin}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.WADS.2025.13}, URN = {urn:nbn:de:0030-drops-242446}, doi = {10.4230/LIPIcs.WADS.2025.13}, annote = {Keywords: diameter, mean distance, continuous graph, treewidth, planar graph} }
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