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Finite Automata Section 1.1 CSC 4170 Theory of Computation

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How a finite automaton works 1.1.a q2q2 q0q0 q1q1 0 0 0 1 11 0 1 1 0 0

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The language of a machine 1.1.b q2q2 q0q0 q1q1 0 0 0 1 11 L(M), “the language of M”, or “the language recognized by M” --- the set all strings that the machine M accepts What is the language recognized by our automaton A? L(A) =

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Formal definition of a finite automaton 1.1.c A finite automaton is a 5-tuple (Q, , , s, F), where: Q is a finite set called the states, is a finite set called the alphabet, is a function of the type Q Q called the transition function, s is an element of Q called the start state, F is a subset of Q called the set of accept states.

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Our automaton formalized 1.1.d q2q2 q0q0 q1q1 0 0 0 1 11 Q:::s:F:Q:::s:F: A = (Q, , , s, F)

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Formal definition of accepting 1.1.e M = (Q, , , s, F) M accepts the string u 1 u 2 … u n iff there is a sequence r 1, r 2, …, r n, r n+1 of states such that: r 1 =s r i+1 = (r i,u i ), for each i with 1 i n r n+1 F q2q2 q0q0 q1q1 0 0 1 11 0 1 1 0 0 u 1 u 2 … u n r 1, r 2, …, r n, r n+1 0

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Designing finite automata 1.1.f Task: Design an automaton that accepts a bit string iff it contains an even number of “1”s.

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Designing finite automata 1.1.g Task: Design an automaton that accepts a bit string iff the number of “1”s that it contains is divisible by 3.

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Designing finite automata 1.1.h Task: Let L2={w | w is a string of 0s whose length is divisible by 2} and L3={w | w is a string of 0s whose length is divisible by 3} Design an automaton that recognizes L2 L3

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Designing finite automata 1.1.i Task: Let L2={w | w is a string of 0s whose length is divisible by 2} and L3={w | w is a string of 0s whose length is divisible by 3} Design an automaton that recognizes L2 L3

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Designing finite automata 1.1.j Task: Design an automaton that recognizes the language X={w | w is a string of 0s whose length is divisible neither by 2 nor by 3} Definition: Let L be a language over an alphabet . The complement of L is the language {w | w is a string over such that w L}. X is the complement of what language?

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