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This article explores the concept of Nondeterministic Finite Acceptors (NFA), explaining their structure and functioning. An NFA accepts a string if a computation exists that leads to acceptance, even with multiple possible transitions for the input alphabet. The discussion includes key examples demonstrating how strings are accepted or rejected in NFAs, particularly highlighting lambda transitions where the read head does not move. Additionally, it offers a formal definition covering states, input alphabet, transition functions, and acceptance criteria.
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Nondeterministic Finite Accepter (NFA) Alphabet =
Nondeterministic Finite Accepter (NFA) Alphabet = Two choices
Nondeterministic Finite Accepter (NFA) Alphabet = Two choices No transition No transition
First Choice “accept”
Second Choice No transition: the automaton hangs
Second Choice “reject”
Observation An NFA accepts a string if there is a computation of the NFA that accepts the string
Example is accepted by the NFA:
“accept” String is accepted
Formal Definition of NFAs Set of states, i.e. Input aplhabet, i.e. Transition function Initial state Final states
Formally It holds if and only if there is a walk from to with label