Testing Quasiperiodicity

Published: 2025, Last Modified: 13 Jan 2026CoRR 2025EveryoneRevisionsBibTeXCC BY-SA 4.0
Abstract: A cover (or quasiperiod) of a string $S$ is a shorter string $C$ such that every position of $S$ is contained in some occurrence of $C$ as a substring. The notion of covers was introduced by Apostolico and Ehrenfeucht over 30 years ago [Theor. Comput. Sci. 1993] and it has received significant attention from the combinatorial pattern matching community. In this note, we show how to efficiently test whether $S$ admits a cover. Our tester can also be translated into a streaming algorithm.
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