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Finding small patterns in permutations in linear time

2013/07/11 by Sylvain Guillemot, Dániel Marx, Guillemot, Sylvain +1 · 6 citations
Computer Science · Engineering · #Algorithms and Data Compression #Cellular Automata and Applications #Data Structures and Algorithms (cs.DS) #Discrete Mathematics (cs.DM) #FOS: Computer and information sciences #cs.DM #cs.DS #graph theory and CDMA systems

paper · pdf · doi:10.48550/arxiv.1307.3073

openalex publication_date 2013/07/11 · arxiv created 2013/10/31 · arxiv updated 2013/11/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

Given two permutations σ and π, the Permutation Pattern problem asks if σ is a subpattern of π. We show that the problem can be solved in time 2O(ℓ2log ℓ)⋅ n, where ℓ=|σ| and n=|π|. In other words, the problem is fixed-parameter tractable parameterized by the size of the subpattern to be found. We introduce a novel type of decompositions for permutations and a corresponding width measure. We present a linear-time algorithm that either finds σ as a subpattern of π, or finds a decomposition of π whose width is bounded by a function of |σ|. Then we show how to solve the Permutation Pattern problem in linear time if a bounded-width decomposition is given in the input.

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