Computing the Longest Previous Factor
Abstract
The Longest Previous Factor array gives, for each position i in a string y, the length of the longest factor (substring) of y that occurs both at i and to the left of i in y. The Longest Previous Factor array is central in many text compression techniques as well as in the most efficient algorithms for detecting motifs and repetitions occurring in a text. Computing the Longest Previous Factor array requires usually the Suffix Array and the Longest Common Prefix array. We give the first time-space optimal algorithm that computes the Longest Previous Factor array, given the Suffix Array and the Longest Common Prefix arrays. We also give the first linear-time algorithm that computes the permutation that applied to the Longest Common Prefix array produces the Longest Previous Factor array.
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