文章基本信息

标题：Optimal Reachability and a Space-Time Tradeoff for Distance Queries in Constant-Treewidth Graphs
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作者：Krishnendu Chatterjee ; Rasmus Rasmus Ibsen-Jensen ; Andreas Pavlogiannis 等
期刊名称：LIPIcs : Leibniz International Proceedings in Informatics
电子版ISSN：1868-8969
出版年度：2016
卷号：57
页码：28:1-28:17
DOI：10.4230/LIPIcs.ESA.2016.28
出版社：Schloss Dagstuhl -- Leibniz-Zentrum fuer Informatik
摘要：We consider data-structures for answering reachability and distance queries on constant-treewidth graphs with n nodes, on the standard RAM computational model with wordsize W=Theta(log n). Our first contribution is a data-structure that after O(n) preprocessing time, allows (1) pair reachability queries in O(1) time; and (2) single-source reachability queries in O(n/log n) time. This is (asymptotically) optimal and is faster than DFS/BFS when answering more than a constant number of single-source queries. The data-structure uses at all times O(n) space. Our second contribution is a space-time tradeoff data-structure for distance queries. For any epsilon in [1/2,1], we provide a data-structure with polynomial preprocessing time that allows pair queries in O(n^{1-\epsilon} alpha(n)) time, where alpha is the inverse of the Ackermann function, and at all times uses O(n^epsilon) space. The input graph G is not considered in the space complexity.
关键词：Graph algorithms; Constant-treewidth graphs; Reachability queries; Distance queries