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arXiv · 2606.31030

Optimal-Time Contextual Pattern Matching in Compressed Space

Gonzalo Navarro·Francisco Olivares
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Abstract

Contextual pattern matching is the task of, given a pattern $P[1,m]$, a context length $λ$, and a text $T[1,n]$, find all the $occ$ distinct contexts in which $P$ occurs in $T$, the context being the $λ$ symbols preceding and the $λ$ symbols following the occurrence; a text position where each context occurs must be output. While the problem can be solved in optimal time $O(m+occ)$ using $O(n)$-space precomputed data structures on $T$, this type of search is particularly relevant on large repetitive text collections, where $O(n)$ space can be prohibitive. We present the first optimal-time solution that runs in compressed space, namely that of a symmetric CDAWG (SCDAWG) of $T$. Further, we show how the set of $occ$ solutions can be enumerated with $O(\log\logλ)$ delay after $O(m)$-time preprocessing of $P$. To achieve this, we develop an improved linear-space distance-sensitive weighted ancestor data structure.

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Gonzalo Navarro, Francisco Olivares. 2026-08-21. Optimal-Time Contextual Pattern Matching in Compressed Space. https://arxiv.org/abs/2606.31030

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