2026-07-23T22:21:20Z https://drops.dagstuhl.de/oai

oai:drops-oai.dagstuhl.de:16980 2024-03-06T10:58:52Z ddc:004 open_access

Near Optimal Algorithm for Fault Tolerant Distance Oracle and Single Source Replacement Path Problem Dey, Dipan Gupta, Manoj distance sensitivity oracle single-source replacement paths In a graph G with a source s, we design a distance oracle that can answer the following query: Query(s,t,e) - find the length of shortest path from a fixed source s to any destination vertex t while avoiding any edge e. We design a deterministic algorithm that builds such an oracle in Õ(m √n) time. Our oracle uses Õ(n √n) space and can answer queries in Õ(1) time. Our oracle is an improvement of the work of Bilò et al. (ESA 2021) in the preprocessing time, which constructs the first deterministic oracle for this problem in Õ(m √n+n²) time. Using our distance oracle, we also solve the single source replacement path problem (Ssrp problem). Chechik and Cohen (SODA 2019) designed a randomized combinatorial algorithm to solve the Ssrp problem. The running time of their algorithm is Õ(m √n + n²). In this paper, we show that the Ssrp problem can be solved in Õ(m √n + |ℛ|) time, where ℛ is the output set of the Ssrp problem in G. Our Ssrp algorithm is optimal (upto polylogarithmic factor) as there is a conditional lower bound of Ω(m √n) for any combinatorial algorithm that solves this problem. Schloss Dagstuhl – Leibniz-Zentrum für Informatik Dipan Dey and Manoj Gupta 2022 Is Part Of LIPIcs, Volume 244, 30th Annual European Symposium on Algorithms (ESA 2022) InProceedings Text doc-type:ResearchArticle publishedVersion application/pdf doi:10.4230/LIPIcs.ESA.2022.42 urn:nbn:de:0030-drops-169800 https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2022.42 eng https://creativecommons.org/licenses/by/4.0/legalcode