Fully dynamic algorithms for maintaining all-pairs shortest paths and transitive closure in digraphs 论文

摘要

This paper presents the first fully dynamic algorithms for maintaining all-pairs shortest paths in digraphs with positive integer weights less than b. For approximate shortest paths with an error factor of (2+/spl epsiv/), for any positive constant /spl epsiv/, the amortized update time is O(n/sup 2/ log/sup 2/ n/log log n); for an error factor of (1+/spl epsiv/) the amortized update time is O(n/sup 2/ log/sup 3/ (bn)//spl epsiv//sup 2/). For exact shortest paths the amortized update time is O(n/sup 2.5/ /spl radic/(b log n)). Query time for exact and approximate shortest distances is O(1); exact time and approximate paths can be generated in time proportional to their lengths. Also presented is a fully dynamic transitive closure algorithm with update time O(n/sup 2/ log n) and query time O(1). The previously known fully dynamic transitive closure algorithm with fast query time has one-sided error and update time O(n/sup 2.28/). The algorithms use simple data structures, and are deterministic.