Sublinear Time Shortest Path in Expander Graphs

  • Noga Alon*
  • , Allan Grønlund*
  • , Søren Fuglede Jørgensen*
  • , Kasper Green Larsen*
  • *Corresponding author for this work

Research output: Contribution to book/anthology/report/proceedingArticle in proceedingsResearchpeer-review

Abstract

Computing a shortest path between two nodes in an undirected unweighted graph is among the most basic algorithmic tasks. Breadth first search solves this problem in linear time, which is clearly also a lower bound in the worst case. However, several works have shown how to solve this problem in sublinear time in expectation when the input graph is drawn from one of several classes of random graphs. In this work, we extend these results by giving sublinear time shortest path (and short path) algorithms for expander graphs. We thus identify a natural deterministic property of a graph (that is satisfied by typical random regular graphs) which suffices for sublinear time shortest paths. The algorithms are very simple, involving only bidirectional breadth first search and short random walks. We also complement our new algorithms by near-matching lower bounds.

Original languageEnglish
Title of host publication49th International Symposium on Mathematical Foundations of Computer Science, MFCS 2024
EditorsRastislav Kralovic, Antonin Kucera
PublisherDagstuhl Publishing
Publication dateAug 2024
Pages8:1-8:13
Article number8
ISBN (Electronic)9783959773355
DOIs
Publication statusPublished - Aug 2024
Event49th International Symposium on Mathematical Foundations of Computer Science, MFCS 2024 - Bratislava, Slovakia
Duration: 26 Aug 202430 Aug 2024

Conference

Conference49th International Symposium on Mathematical Foundations of Computer Science, MFCS 2024
Country/TerritorySlovakia
CityBratislava
Period26/08/202430/08/2024
SeriesLeibniz International Proceedings in Informatics, LIPIcs
Volume306
ISSN1868-8969

Keywords

  • Breadth First Search
  • Expanders
  • Graph Algorithms
  • Shortest Path

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