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We study how the application of injective morphisms affects the number $r$ of equal-letter runs in the Burrows-Wheeler Transform (BWT). This parameter has emerged as a key repetitiveness measure in compressed indexing. We focus on the…

Formal Languages and Automata Theory · Computer Science 2025-04-25 Gabriele Fici , Giuseppe Romana , Marinella Sciortino , Cristian Urbina

Indexing highly repetitive strings (i.e., strings with many repetitions) for fast queries has become a central research topic in string processing, because it has a wide variety of applications in bioinformatics and natural language…

Data Structures and Algorithms · Computer Science 2021-04-19 Takaaki Nishimoto , Yasuo Tabei

The compression of highly repetitive strings (i.e., strings with many repetitions) has been a central research topic in string processing, and quite a few compression methods for these strings have been proposed thus far. Among them, an…

Data Structures and Algorithms · Computer Science 2022-02-17 Takaaki Nishimoto , Shunsuke Kanda , Yasuo Tabei

We propose algorithms that, given the input string of length $n$ over integer alphabet of size $\sigma$, construct the Burrows-Wheeler transform (BWT), the permuted longest-common-prefix (PLCP) array, and the LZ77 parsing in…

Data Structures and Algorithms · Computer Science 2020-12-09 Dominik Kempa

The Positional Burrows--Wheeler Transform (PBWT) is a data structure designed for efficiently representing and querying large collections of sequences, such as haplotype panels in genomics. Forward and backward stepping operations --…

Data Structures and Algorithms · Computer Science 2026-02-17 Paola Bonizzoni , Davide Cozzi , Younan Gao

The field of succinct data structures has flourished over the last 16 years. Starting from the compressed suffix array (CSA) by Grossi and Vitter (STOC 2000) and the FM-index by Ferragina and Manzini (FOCS 2000), a number of generalizations…

Data Structures and Algorithms · Computer Science 2016-09-22 Djamal Belazzougui , Fabio Cunial , Juha Kärkkäinen , Veli Mäkinen

A weight based dynamic compression method has recently been proposed, which is especially suitable for the encoding of files with locally skewed distributions. Its main idea is to assign larger weights to closer to be encoded symbols by…

Data Structures and Algorithms · Computer Science 2021-05-24 Aharon Fruchtman , Yoav Gross , Shmuel T. Klein , Dana Shapira

We survey the different methods used for extending the BWT to collections of strings, following largely [Cenzato and Lipt\'ak, CPM 2022, Bioinformatics 2024]. We analyze the specific aspects and combinatorial properties of the resulting BWT…

Data Structures and Algorithms · Computer Science 2025-06-03 Davide Cenzato , Zsuzsanna Lipták , Nadia Pisanti , Giovanna Rosone , Marinella Sciortino

In this paper we study the number $r_{bwt}$ of equal-letter runs produced by the Burrows-Wheeler transform ($BWT$) when it is applied to purely morphic finite words, which are words generated by iterating prolongable morphisms. Such a…

Formal Languages and Automata Theory · Computer Science 2022-02-08 Andrea Frosini , Ilaria Mancini , Simone Rinaldi , Giuseppe Romana , Marinella Sciortino

Indexing of very large collections of strings such as those produced by the widespread sequencing technologies, heavily relies on multi-string generalizations of the Burrows-Wheeler Transform (BWT), and for this problem various in-memory…

Data Structures and Algorithms · Computer Science 2016-07-29 Paola Bonizzoni , Gianluca Della Vedova , Serena Nicosia , Marco Previtali , Raffaella Rizzi

In this article we extend the elegant in-place Burrows-Wheeler transform (BWT) algorithm proposed by Crochemore et al. (Crochemore et al., 2015). Our extension is twofold: we first show how to compute simultaneously the longest common…

Data Structures and Algorithms · Computer Science 2018-06-08 Felipe A. Louza , Travis Gagie , Guilherme P. Telles

Popular sequence alignment tools such as BWA convert a reference genome to an indexing data structure based on the Burrows-Wheeler Transform (BWT), from which matches to individual query sequences can be rapidly determined. However the…

Genomics · Quantitative Biology 2013-04-23 Anthony J. Cox , Tobias Jakobi , Giovanna Rosone , Ole B. Schulz-Trieglaff

Given a string $T$ on an alphabet of size $\sigma$, we describe a bidirectional Burrows-Wheeler index that takes $O(|T|\log{\sigma})$ bits of space, and that supports the addition \emph{and removal} of one character, on the left or right…

Data Structures and Algorithms · Computer Science 2019-06-11 Fabio Cunial , Djamal Belazzougui

The notion of Wheeler languages is rooted in the Burrows-Wheeler transform (BWT), one of the most central concepts in data compression and indexing. The BWT has been generalized to finite automata, the so-called Wheeler automata, by Gagie…

Formal Languages and Automata Theory · Computer Science 2025-04-29 Ruben Becker , Giuseppa Castiglione , Giovanna D'Agostino , Alberto Policriti , Nicola Prezza , Antonio Restivo , Brian Riccardi

Motivation: Burrows-Wheeler Transform (BWT) is a common component in full-text indices. Initially developed for data compression, it is particularly powerful for encoding redundant sequences such as pangenome data. However, BWT construction…

Genomics · Quantitative Biology 2025-09-10 Heng Li

Detecting all the strings that occur in a text more frequently or less frequently than expected according to an IID or a Markov model is a basic problem in string mining, yet current algorithms are based on data structures that are either…

Data Structures and Algorithms · Computer Science 2015-08-13 Djamal Belazzougui , Fabio Cunial

The positional Burrows-Wheeler Transform (PBWT) is commonly used to store haplotype panels compactly in such a way that, given a query haplotype, we can quickly find the set maximal exact matches (SMEMs) between the query and the haplotypes…

Data Structures and Algorithms · Computer Science 2026-05-26 Travis Gagie

We study the impact that string reversal can have on several repetitiveness measures. First, we exhibit an infinite family of strings where the number, $r$, of runs in the run-length encoding of the Burrows--Wheeler transform (BWT) can…

Data Structures and Algorithms · Computer Science 2026-02-17 Hideo Bannai , Yuto Fujie , Peaker Guo , Shunsuke Inenaga , Yuto Nakashima , Simon J. Puglisi , Cristian Urbina

We show how to merge two run-length compressed Burrows-Wheeler Transforms (RLBWTs) into a run-length compressed extended Burrows-Wheeler Transform (eBWT) in $O (r)$ space and $O ((r + L) \log (m + n))$ time, where $m$ and $n$ are the…

Data Structures and Algorithms · Computer Science 2026-04-16 Travis Gagie

Mantaci et al. [TCS 2007] defined the eBWT to extend the definition of the BWT to a collection of strings, however, since this introduction, it has been used more generally to describe any BWT of a collection of strings and the fundamental…

Data Structures and Algorithms · Computer Science 2021-06-22 Christina Boucher , Davide Cenzato , Zsuzsanna Lipták , Massimiliano Rossi , Marinella Sciortino