Position-restricted substring searching over small alphabets

Authors

Sudip Biswas, National Tsing Hua University
Tsung Han Ku, National Tsing Hua University
Rahul Shah, LSU College of Engineering
Sharma V. Thankachan, College of Engineering and Computer Science

Document Type

Article

Publication Date

9-1-2017

Abstract

We consider the problem of indexing a given text T[0n−1] of n characters over an alphabet set Σ of size σ, in order to answer the position-restricted substring searching queries. The query input consists of a pattern P (of length p) and two indices ℓ and r and the output is the set of all occℓ,r occurrences of P in T[ℓr]. In this paper, we propose an O(nlog⁡σ)-word space index with O(p+occℓ,rlog⁡log⁡n) query time. Our solution is interesting when the alphabet size is small. For example, when the alphabet set is of constant size, we achieve significant improvement over the previously best-known linear space index by Navarro and Nekrich [SWAT 2012] with O(p+occℓ,rlogϵ⁡n) query time, where ϵ>0 is an arbitrarily small positive constant.

Publication Source (Journal or Book title)

Journal of Discrete Algorithms

First Page

36

Last Page

39

Recommended Citation

Biswas, S., Ku, T., Shah, R., & Thankachan, S. (2017). Position-restricted substring searching over small alphabets. Journal of Discrete Algorithms, 46-47, 36-39. https://doi.org/10.1016/j.jda.2017.10.001