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An LZ-like factorization of a string divides it into factors, each being either a single character or a copy of a preceding substring. While grammar-based compression schemes support efficient random access with space linear in the…

Data Structures and Algorithms · Computer Science 2026-01-22 Hiroki Shibata , Yuto Nakashima , Yutaro Yamaguchi , Shunsuke Inenaga

We address the problem of compressed sensing (CS) with prior information: reconstruct a target CS signal with the aid of a similar signal that is known beforehand, our prior information. We integrate the additional knowledge of the similar…

Information Theory · Computer Science 2014-08-25 Joao F. C. Mota , Nikos Deligiannis , Miguel R. D. Rodrigues

This paper deals with the design of a sensing matrix along with a sparse recovery algorithm by utilizing the probability-based prior information for compressed sensing system. With the knowledge of the probability for each atom of the…

Machine Learning · Computer Science 2019-10-29 Q. Jiang , S. Li , Z. Zhu , H. Bai , X. He , R. C. de Lamare

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

We present an algorithm that constructs the LZ-End parsing (a variation of LZ77) of a given string of length $n$ in $O(n\log\ell)$ expected time and $O(z + \ell)$ space, where $z$ is the number of phrases in the parsing and $\ell$ is the…

Data Structures and Algorithms · Computer Science 2020-12-15 Dominik Kempa , Dmitry Kosolobov

We consider the problem of encoding a string of length $n$ from an integer alphabet of size $\sigma$ so that access and substring equality queries (that is, determining the equality of any two substrings) can be answered efficiently. Any…

Data Structures and Algorithms · Computer Science 2020-05-12 Nicola Prezza

The suffix array and the suffix tree are the two most fundamental data structures for string processing. For a length-$n$ text, however, they use $\Theta(n \log n)$ bits of space, which is often too costly. To address this, Grossi and…

Data Structures and Algorithms · Computer Science 2023-04-20 Dominik Kempa , Tomasz Kociumaka

Given a pattern string $P$ of length $n$ and a query string $T$ of length $m$, where the characters of $P$ and $T$ are drawn from an alphabet of size $\Delta$, the {\em exact string matching} problem consists of finding all occurrences of…

Data Structures and Algorithms · Computer Science 2015-10-01 Srikrishnan Divakaran

Text indexing is a fundamental and well-studied problem. Classic solutions either replace the original text with a compressed representation, e.g., the FM-index and its variants, or keep it uncompressed but attach some redundancy - an index…

Data Structures and Algorithms · Computer Science 2026-02-05 Lorraine A. K. Ayad , Gabriele Fici , Ragnar Groot Koerkamp , Grigorios Loukides , Rob Patro , Giulio Ermanno Pibiri , Solon P. Pissis

In this paper, we propose a novel approach to combine \emph{compact directed acyclic word graphs} (CDAWGs) and grammar-based compression. This leads us to an efficient self-index, called Linear-size CDAWGs (L-CDAWGs), which can be…

Data Structures and Algorithms · Computer Science 2017-07-28 Takuya Takagi , Keisuke Goto , Yuta Fujishige , Shunsuke Inenaga , Hiroki Arimura

Given a text $T$ of length $n$ and a pattern $P$ of length $m$, the string matching problem is a task to find all occurrences of $P$ in $T$. In this study, we propose an algorithm that solves this problem in $O((n + m)q)$ time considering…

Data Structures and Algorithms · Computer Science 2020-04-14 Satoshi Kobayashi , Diptarama Hendrian , Ryo Yoshinaka , Ayumi Shinohara

Many large-scale Web applications that require ranked top-k retrieval such as Web search and online advertising are implemented using inverted indices. An inverted index represents a sparse term-document matrix, where non-zero elements…

Information Retrieval · Computer Science 2015-03-19 George Beskales , Marcus Fontoura , Maxim Gurevich , Sergei Vassilvitskii , Vanja Josifovski

Consider the problem of recovering an unknown signal from undersampled measurements, given the knowledge that the signal has a sparse representation in a specified dictionary $D$. This problem is now understood to be well-posed and…

Information Theory · Computer Science 2015-06-09 Felix Krahmer , Deanna Needell , Rachel Ward

Compressed sensing is a novel technique where one can recover sparse signals from the undersampled measurements. In this paper, a $K \times N$ measurement matrix for compressed sensing is deterministically constructed via multiplicative…

Information Theory · Computer Science 2010-11-12 Nam Yul Yu

In the dynamic indexing problem, we must maintain a changing collection of text documents so that we can efficiently support insertions, deletions, and pattern matching queries. We are especially interested in developing efficient data…

Data Structures and Algorithms · Computer Science 2015-03-23 J. Ian Munro , Yakov Nekrich , Jeffrey Scott Vitter

We show how to determine whether a given pattern p of length m occurs in a given text t of length n in ${\tilde O}(\sqrt{n}+\sqrt{m})$\footnote{${\tilde O}$ allows for logarithmic factors in m and $n/m$} time, with inverse polynomial…

Quantum Physics · Physics 2007-05-23 H. Ramesh , V. Vinay

Bille and G{\o}rtz (2011) recently introduced the problem of substring range counting, for which we are asked to store compactly a string $S$ of $n$ characters with integer labels in ([0, u]), such that later, given an interval ([a, b]) and…

Data Structures and Algorithms · Computer Science 2012-02-16 Travis Gagie , Paweł Gawrychowski

Compressed sensing is a technique for finding sparse solutions to underdetermined linear systems. This technique relies on properties of the sensing matrix such as the restricted isometry property. Sensing matrices that satisfy the…

Computational Complexity · Computer Science 2011-10-18 Pascal Koiran , Anastasios Zouzias

It is widely assumed that $O(m+\lg \sigma)$ is the best one can do for finding a pattern of length $m$ in a compacted trie storing strings over an alphabet of size $\sigma$, if one insists on linear-size data structures and deterministic…

Data Structures and Algorithms · Computer Science 2013-02-15 Johannes Fischer , Pawel Gawrychowski

Recently Kubica et al. (Inf. Process. Let., 2013) and Kim et al. (submitted to Theor. Comp. Sci.) introduced order-preserving pattern matching. In this problem we are looking for consecutive substrings of the text that have the same "shape"…