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A classical measure of string comparison is given by the longest common subsequence (LCS) problem on a pair of strings. We consider its generalisation, called the semi-local LCS problem, which arises naturally in many string-related…

Data Structures and Algorithms · Computer Science 2015-03-13 Alexander Tiskin

In this work, we revisit the fundamental and well-studied problem of approximate pattern matching under edit distance. Given an integer $k$, a pattern $P$ of length $m$, and a text $T$ of length $n \ge m$, the task is to find substrings of…

Data Structures and Algorithms · Computer Science 2021-06-14 Tomasz Kociumaka , Ely Porat , Tatiana Starikovskaya

The string indexing problem is a fundamental computational problem with numerous applications, including information retrieval and bioinformatics. It aims to efficiently solve the pattern matching problem: given a text T of length n for…

Data Structures and Algorithms · Computer Science 2025-09-03 Waseem Akram , Takuya Mieno

We consider a range of simply stated dynamic data structure problems on strings. An update changes one symbol in the input and a query asks us to compute some function of the pattern of length $m$ and a substring of a longer text. We give…

Data Structures and Algorithms · Computer Science 2018-02-20 Raphael Clifford , Allan Grønlund , Kasper Green Larsen , Tatiana Starikovskaya

In this paper, we consider a generalized longest common subsequence problem, the string-excluding constrained LCS problem. For the two input sequences $X$ and $Y$ of lengths $n$ and $m$, and a constraint string $P$ of length $r$, the…

Data Structures and Algorithms · Computer Science 2013-01-31 Lei Wang , Xiaodong Wang , Yingjie Wu , Daxin Zhu

We generalize Karp-Rabin string matching to handle multiple patterns in $\mathcal{O}(n \log n + m)$ time and $\mathcal{O}(s)$ space, where $n$ is the length of the text and $m$ is the total length of the $s$ patterns, returning correct…

Data Structures and Algorithms · Computer Science 2015-09-11 Johannes Fischer , Travis Gagie , Paweł Gawrychowski , Tomasz Kociumaka

We consider the approximate pattern matching problem under the edit distance. Given a text $T$ of length $n$, a pattern $P$ of length $m$, and a threshold $k$, the task is to find the starting positions of all substrings of $T$ that can be…

Data Structures and Algorithms · Computer Science 2022-04-08 Panagiotis Charalampopoulos , Tomasz Kociumaka , Philip Wellnitz

Two important similarity measures between sequences are the longest common subsequence (LCS) and the dynamic time warping distance (DTWD). The computations of these measures for two given sequences are central tasks in a variety of…

Computational Complexity · Computer Science 2015-02-02 Amir Abboud , Arturs Backurs , Virginia Vassilevska Williams

We study sketching and streaming algorithms for the Longest Common Subsequence problem (LCS) on strings of small alphabet size $|\Sigma|$. For the problem of deciding whether the LCS of strings $x,y$ has length at least $L$, we obtain a…

Data Structures and Algorithms · Computer Science 2018-10-03 Karl Bringmann , Bhaskar Ray Chaudhury

Text-to-pattern distance is a fundamental problem in string matching, where given a pattern of length $m$ and a text of length $n$, over an integer alphabet, we are asked to compute the distance between pattern and the text at every…

Data Structures and Algorithms · Computer Science 2020-05-04 Przemysław Uznański

We describe how, given a text $T [1..n]$ and a positive constant $\epsilon$, we can build a simple $O (z \log n)$-space index, where $z$ is the number of phrases in the LZ77 parse of $T$, such that later, given a pattern $P [1..m]$, in $O…

Data Structures and Algorithms · Computer Science 2022-12-06 Nick Fagan , Jorge Hermo González , Travis Gagie

We study the problem of computing a longest increasing subsequence in a sequence $S$ of $n$ distinct elements in the presence of persistent comparison errors. In this model, every comparison between two elements can return the wrong result…

Data Structures and Algorithms · Computer Science 2018-08-13 Barbara Geissmann

We study the problem of finding all $k$-periods of a length-$n$ string $S$, presented as a data stream. $S$ is said to have $k$-period $p$ if its prefix of length $n-p$ differs from its suffix of length $n-p$ in at most $k$ locations. We…

Data Structures and Algorithms · Computer Science 2017-08-16 Funda Ergün , Elena Grigorescu , Erfan Sadeqi Azer , Samson Zhou

For any given $\epsilon>0$ we provide an algorithm for the Densest $k$-Subhypergraph Problem with an approximation ratio of at most $O(n^{\theta_m+2\epsilon})$ for $\theta_m=\frac{1}{2}m-\frac{1}{2}-\frac{1}{2m}$ and run time at most…

Data Structures and Algorithms · Computer Science 2016-10-18 Richard Taylor

The classic string indexing problem is to preprocess a string S into a compact data structure that supports efficient pattern matching queries. Typical queries include existential queries (decide if the pattern occurs in S), reporting…

Data Structures and Algorithms · Computer Science 2021-02-05 Philip Bille , Inge Li Gørtz , Max Rishøj Pedersen , Teresa Anna Steiner

Palindromes are strings that read the same forward and backward. The computation of palindromic structures within strings is a fundamental problem in string algorithms, being motivated by potential applications in formal language theory and…

Data Structures and Algorithms · Computer Science 2026-05-15 Takuya Mieno , Tomohiro I

We introduce a new string matching problem called order-preserving matching on numeric strings where a pattern matches a text if the text contains a substring whose relative orders coincide with those of the pattern. Order-preserving…

Data Structures and Algorithms · Computer Science 2013-02-19 Jinil Kim , Peter Eades , Rudolf Fleischer , Seok-Hee Hong , Costas S. Iliopoulos , Kunsoo Park , Simon J. Puglisi , Takeshi Tokuyama

The longest common extension problem is to preprocess a given string of length $n$ into a data structure that uses $S(n)$ bits on top of the input and answers in $T(n)$ time the queries $\mathit{LCE}(i,j)$ computing the length of the…

Data Structures and Algorithms · Computer Science 2017-05-12 Dmitry Kosolobov

We consider a class of pattern matching problems where a normalising transformation is applied at every alignment. Normalised pattern matching plays a key role in fields as diverse as image processing and musical information processing…

Data Structures and Algorithms · Computer Science 2015-03-19 Ayelet Butman , Peter Clifford , Raphael Clifford , Markus Jalsenius , Noa Lewenstein , Benny Porat , Ely Porat , Benjamin Sach

We revisit the task of computing the edit distance in sublinear time. In the $(k,K)$-gap edit distance problem the task is to distinguish whether the edit distance of two strings is at most $k$ or at least $K$. It has been established by…

Data Structures and Algorithms · Computer Science 2023-03-17 Karl Bringmann , Alejandro Cassis , Nick Fischer , Vasileios Nakos