O~(n^{1/3})-Space Algorithm for the Grid Graph Reachability Problem

Authors Ryo Ashida, Kotaro Nakagawa

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Ryo Ashida
Kotaro Nakagawa

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Ryo Ashida and Kotaro Nakagawa. O~(n^{1/3})-Space Algorithm for the Grid Graph Reachability Problem. In 34th International Symposium on Computational Geometry (SoCG 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 99, pp. 5:1-5:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)


The directed graph reachability problem takes as input an n-vertex directed graph G=(V,E), and two distinguished vertices s and t. The problem is to determine whether there exists a path from s to t in G. This is a canonical complete problem for class NL. Asano et al. proposed an O~(sqrt{n}) space and polynomial time algorithm for the directed grid and planar graph reachability problem. The main result of this paper is to show that the directed graph reachability problem restricted to grid graphs can be solved in polynomial time using only O~(n^{1/3}) space.
  • graph reachability
  • grid graph
  • graph algorithm
  • sublinear space algorithm


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