Absent Subsequences in Words

An absent factor of a string w is u which does not occur as contiguous substring (a.k.a. factor) inside w. We extend this well-studied notion and define subsequences: an subsequence if scattered Of particular interest to us are minimal subsequences, i.e., subsequences whose every absent, shortest length. show series combinatorial algorithmic results regarding these two notions. For instance: we give characterisations the sets and, respectively, in word, well compact representations sets; how can test efficiently or efficient algorithms computing lexicographically smallest each kind; also, data structure for answering subsequence-queries factors given be computed.