On the State Complexity of Scattered Substrings and Superstrings

被引:13
作者
Okhotin, Alexander [1 ,2 ]
机构
[1] Univ Turku, Dept Math, FIN-20014 Turku, Finland
[2] Acad Finland, Helsinki, Finland
基金
芬兰科学院;
关键词
descriptional complexity; finite automata; state complexity; substring; subword; subsequence; Higman-Haines sets; HIGMAN-HAINES SETS; REGULAR LANGUAGES; EFFECTIVE CONSTRUCTIONS; OPERATIONS; SIZE;
D O I
10.3233/FI-2010-252
中图分类号
TP31 [计算机软件];
学科分类号
081202 ; 0835 ;
摘要
It is proved that the set of scattered substrings of a language recognized by an n-state DFA requires a DFA with at least 2(n/2-2) states (the known upper bound is 2(n)), with witness languages given over an exponentially growing alphabet. For a 3-letter alphabet, scattered substrings are shown to require at least 2(root 2n+30-6) states. A similar state complexity function for scattered superstrings is determined to be exactly 2(n-2) + 1 for an alphabet of at least n-2 letters, and strictly less for any smaller alphabet. For a 3-letter alphabet, the state complexity of scattered superstrings is at least 1/54(root n/2)n(-3/4).
引用
收藏
页码:325 / 338
页数:14
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