Creative Commons Attribution 4.0 International license
We present the first truly subquadratic time algorithm to compute diameter and eccentricities in real-weighted directed graphs with constant distance VC-dimension and strongly sublinear-sized balanced separators. For real-weighted K_h-minor-free digraphs, this runs in O(n^{2-1/(2h-2)} polylog(n)) time.
Prior to this work, truly subquadratic time computation of diameter was only known for real-weighted planar graphs, while extensions to broader classes like minor-free graphs were restricted to unweighted settings. In particular, existing algorithms that use VC-dimension [Ducoffe, Habib, Viennot; SICOMP 2022] [Le, Wulff-Nilsen; SODA 2024] [Chan, Chang, Gao, Le, Kisfaludi-Bak, Zheng; FOCS 2025] work with small integer weights, but do not naturally generalize to real weights. We overcome this barrier by introducing a randomized search-to-decision reduction, demonstrating that VC-dimension is a sufficiently powerful tool in the real-weighted regime.
@InProceedings{zheng:LIPIcs.ESA.2026.61,
author = {Zheng, Da Wei},
title = {{Real-Weighted Diameter and Eccentricities of Minor-Free and Bounded VC-Dimension Graphs in Truly Subquadratic Time}},
booktitle = {34th Annual European Symposium on Algorithms (ESA 2026)},
pages = {61:1--61:12},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-445-1},
ISSN = {1868-8969},
year = {2026},
volume = {388},
editor = {Bille, Philip and Pettie, Seth and Storandt, Sabine},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2026.61},
URN = {urn:nbn:de:0030-drops-271973},
doi = {10.4230/LIPIcs.ESA.2026.61},
annote = {Keywords: Diameter, eccentricities, minor-free graphs, real weights, VC-dimension}
}