dc.contributor.author | Demaine, Erik D. | |
dc.contributor.author | Huang, Yamming | |
dc.contributor.author | Liao, Chung-Shou | |
dc.contributor.author | Sadakane, Kunihiko | |
dc.date.accessioned | 2015-11-23T15:53:41Z | |
dc.date.available | 2015-11-23T15:53:41Z | |
dc.date.issued | 2014 | |
dc.identifier.isbn | 978-3-662-43947-0 | |
dc.identifier.isbn | 978-3-662-43948-7 | |
dc.identifier.issn | 0302-9743 | |
dc.identifier.issn | 1611-3349 | |
dc.identifier.uri | http://hdl.handle.net/1721.1/99995 | |
dc.description.abstract | We study online algorithms for the Canadian Traveller Problem (CTP) introduced by Papadimitriou and Yannakakis in 1991. In this problem, a traveller knows the entire road network in advance, and wishes to travel as quickly as possible from a source vertex s to a destination vertex t, but discovers online that some roads are blocked (e.g., by snow) once reaching them. It is PSPACE-complete to achieve a bounded competitive ratio for this problem. Furthermore, if at most k roads can be blocked, then the optimal competitive ratio for a deterministic online algorithm is 2k + 1, while the only randomized result known is a lower bound of k + 1.
In this paper, we show for the first time that a polynomial time randomized algorithm can beat the best deterministic algorithms, surpassing the 2k + 1 lower bound by an o(1) factor. Moreover, we prove the randomized algorithm achieving a competitive ratio of (1 + [√2 over 2])k + 1 in pseudo-polynomial time. The proposed techniques can also be applied to implicitly represent multiple near-shortest s-t paths. | en_US |
dc.description.sponsorship | NSC Grant 102-2221-E-007-075-MY3 | en_US |
dc.description.sponsorship | Japan Society for the Promotion of Science (KAKENHI 23240002) | en_US |
dc.language.iso | en_US | |
dc.publisher | Springer-Verlag | en_US |
dc.relation.isversionof | http://dx.doi.org/10.1007/978-3-662-43948-7_32 | en_US |
dc.rights | Creative Commons Attribution-Noncommercial-Share Alike | en_US |
dc.rights.uri | http://creativecommons.org/licenses/by-nc-sa/4.0/ | en_US |
dc.source | MIT web domain | en_US |
dc.title | Canadians Should Travel Randomly | en_US |
dc.type | Article | en_US |
dc.identifier.citation | Demaine, Erik D., Yamming Huang, Chung-Shou Liao, and Kunihiko Sadakane. “Canadians Should Travel Randomly.” Lecture Notes in Computer Science (2014): 380–391. | en_US |
dc.contributor.department | Massachusetts Institute of Technology. Computer Science and Artificial Intelligence Laboratory | en_US |
dc.contributor.department | Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science | en_US |
dc.contributor.mitauthor | Demaine, Erik D. | en_US |
dc.relation.journal | Automata, Languages, and Programming | en_US |
dc.eprint.version | Author's final manuscript | en_US |
dc.type.uri | http://purl.org/eprint/type/ConferencePaper | en_US |
eprint.status | http://purl.org/eprint/status/NonPeerReviewed | en_US |
dspace.orderedauthors | Demaine, Erik D.; Huang, Yamming; Liao, Chung-Shou; Sadakane, Kunihiko | en_US |
dc.identifier.orcid | https://orcid.org/0000-0003-3803-5703 | |
mit.license | OPEN_ACCESS_POLICY | en_US |
mit.metadata.status | Complete | |