Research output: Contribution to journal › Article › peer-review
Unambiguous finite automata over a unary alphabet. / Okhotin, Alexander.
In: Information and Computation, Vol. 212, 01.03.2012, p. 15-36.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Unambiguous finite automata over a unary alphabet
AU - Okhotin, Alexander
PY - 2012/3/1
Y1 - 2012/3/1
N2 - Nondeterministic finite automata (NFA) with at most one accepting computation on every input string are known as unambiguous finite automata (UFA). This paper considers UFAs over a one-letter alphabet, and determines the exact number of states in DFAs needed to represent unary languages recognized by n-state UFAs in terms of a new number-theoretic function g∼. The growth rate of g∼(n), and therefore of the UFA-DFA tradeoff, is estimated as eΘ(n ln2 n3). The conversion of an n-state unary NFA to a UFA requires UFAs with g(n)+O( n2 )=e( 1+o(1))nlnn states, where g(n) is the greatest order of a permutation of n elements, known as Landau's function. In addition, it is shown that representing the complement of n-state unary UFAs requires UFAs with at least n2 -o(1) states in the worst case, while the Kleene star requires up to exactly ( n-1)2 +1 states.
AB - Nondeterministic finite automata (NFA) with at most one accepting computation on every input string are known as unambiguous finite automata (UFA). This paper considers UFAs over a one-letter alphabet, and determines the exact number of states in DFAs needed to represent unary languages recognized by n-state UFAs in terms of a new number-theoretic function g∼. The growth rate of g∼(n), and therefore of the UFA-DFA tradeoff, is estimated as eΘ(n ln2 n3). The conversion of an n-state unary NFA to a UFA requires UFAs with g(n)+O( n2 )=e( 1+o(1))nlnn states, where g(n) is the greatest order of a permutation of n elements, known as Landau's function. In addition, it is shown that representing the complement of n-state unary UFAs requires UFAs with at least n2 -o(1) states in the worst case, while the Kleene star requires up to exactly ( n-1)2 +1 states.
KW - Ambiguity
KW - Descriptional complexity
KW - Finite automata
KW - Landau's function
KW - State complexity
KW - Unary languages
UR - http://www.scopus.com/inward/record.url?scp=84857261182&partnerID=8YFLogxK
U2 - 10.1016/j.ic.2012.01.003
DO - 10.1016/j.ic.2012.01.003
M3 - Article
AN - SCOPUS:84857261182
VL - 212
SP - 15
EP - 36
JO - Information and Computation
JF - Information and Computation
SN - 0890-5401
ER -
ID: 41139943