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dc.contributor.authorJuvvadi, Ramana Raoen_US
dc.date.accessioned2014-03-14T21:10:43Z
dc.date.available2014-03-14T21:10:43Z
dc.date.issued1993-06-05en_US
dc.identifier.otheretd-05042006-164527en_US
dc.identifier.urihttp://hdl.handle.net/10919/37704
dc.description.abstractOne of the most common tasks in many computer applications is the maintenance of a dictionary of words. The three most basic operations on the dictionary are find, insert, and delete. An important data structure that supports these operations is a hash table. On a hash table, a basic operation takes 0 (1) time in the average case and O( n) time in the worst case, where n is the number of words in the dictionary. While an ordinary hash function maps the words in a dictionary to a hash table with collisions, a perfect hash function maps the words in a dictionary to a hash table with no collisions. Thus, perfect hashing is a special case of hashing, in which a find operation takes 0(1) time in the worst case, and an insert or a delete operation takes 0(1) time in the average case and O(n) time in the worst case.

This thesis addresses the following issues: â ¢ Mapping, ordering and searching (MOS) is a successful algorithmic approach to finding perfect hash functions for static dictionaries. Previously, no analysis has been given for the running time of the MOS algorithm. In this thesis, a lower bound is proved on the tradeoff between the time required to find a perfect hash function and the space required to represent the perfect hash function . â ¢ A new algorithm for static dictionaries called the musical chairs(MC) algorithm is developed that is based on ordering the hyperedges of a graph. It is found experimentally that the MC algorithm runs faster than the MOS algorithm in all cases for which the MC algorithm is capable of finding a perfect hash function. â ¢ A new perfect hashing algorithm is developed for dynamic dictionaries. In this algorithm, an insert or a delete operation takes 0(1) time in the average case, and a find operation takes 0(1) time in the worst case. The algorithm is modeled using results from queueing theory . â ¢ An ordering problem from graph theory, motivated by the hypergraph ordering problem in the Me algorithm, is proved to be NP-complete.

en_US
dc.format.mediumBTDen_US
dc.publisherVirginia Techen_US
dc.relation.haspartLD5655.V856_1993.J888.pdfen_US
dc.subjectHashing (Computer science)en_US
dc.subject.lccLD5655.V856 1993.J888en_US
dc.titlePerfect hashing and related problemsen_US
dc.typeDissertationen_US
dc.contributor.departmentComputer Scienceen_US
dc.description.degreePh. D.en_US
thesis.degree.namePh. D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineComputer Scienceen_US
dc.contributor.committeechairHeath, Lenwood S.en_US
dc.contributor.committeememberAllison, Donald C. S.en_US
dc.contributor.committeememberShaffer, Clifford A.en_US
dc.contributor.committeememberFox, Edward Alanen_US
dc.contributor.committeememberSherali, Hanif D.en_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-05042006-164527/en_US
dc.date.sdate2006-05-04en_US
dc.date.rdate2006-05-04
dc.date.adate2006-05-04en_US


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