On demand string sorting over unbounded alphabets

Carmel Kent, Moshe Lewenstein, Dafna Sheinwald

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Scopus citations


On-demand string sorting is the problem of preprocessing a set of n strings to allow subsequent queries of finding the k < n lexicographically smallest strings (and afterwards the next k etc.) This on-demand variant strongly resembles the search engine queries which give you the best k-ranked pages recurringly. We present a data structure that supports this in O(n) preprocessing time, and answers queries in O(log n) time. There is also a cost of O(N) time amortized over all operations, where N is the total length of the strings. Our data structure is a heap of strings, which supports heapify and delete-mins. As it turns out, implementing a full heap with all operations is not that simple. For the sake of completeness we propose a heap with full operations based on balanced indexing trees that supports the heap operations in optimal times.

Original languageEnglish
Title of host publicationCombinatorial Pattern Matching - 18th Annual Symposium, CPM 2007, Proceedings
PublisherSpringer Verlag
Number of pages12
ISBN (Print)9783540734369
StatePublished - 2007
Event18th Annual Symposium on Combinatorial Pattern Matching, CPM 2007 - London, ON, Canada
Duration: 9 Jul 200711 Jul 2007

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume4580 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference18th Annual Symposium on Combinatorial Pattern Matching, CPM 2007
CityLondon, ON


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