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Questions tagged [automata]

In theoretical computer science, automata theory is the study of abstract 'mathematical' machines or systems and the computational problems that can be solved using these machines. These abstract machines are called automata. ("Automata", Wikipedia)

From Wikipedia,

Automata, or automata theory, is the study of mathematical objects called abstract machines or automata and the computational problems that can be solved using them. Automata comes from the Greek word αὐτόματα meaning "self-acting".

692 questions
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Provide a context-free grammar that generates odd length language {w = 0*1* : |w| is odd}

Provide a context-free grammar that generates the following language over Σ = {0,1}: {w = 0*1* : |w| is odd} My Solution: S->AB|0|1 A->0A|^ B->1B|^ But using this grammar we are able to create an even number of string. I want grammar that produces…
Parth Patel
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Find the DFA for the language L given

L is a language over {x,y,z} where x's are never preceded by y's and never followed by z's
Aastha Dahal
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Deterministic finite automaton for even zeroes and ones in multiples of 5

Given a binary string, create a DFA to check if the number of zeroes is even and the number of ones is a multiple of 5.
Avinash Kadimisetty
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Programming an automata

I need to write a script that generates different sentences as Jean sleeps, Jean's mother sleeps, Jean's mother's cousin sleeps. Jean's sister's husband's brother sleeps and so on. For that I wrote a code of eight functions as seen below. Now I…
oezlem
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RegEx Parser like in Automata Class

It seems that most CS textbooks in Automata theory cover Regular Expressions with the alphabet Σ = {0, 1} or Σ = {a, b}. Many students in Automata class had trouble writing RegEx's, is there a parser that accepts something like the following…
rs_user
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Using regular expressions check if a particular segment exist in a given string

There are segments in the below-mentioned string. Each segment is started with a tilt(~) sign and I want to check if there exists a segment in which the AAA segment appears and on its 3rd index a number 63 is present. ISA*ABC**TODAY*ALEXANDER…
Aamerallous
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regular expression for L = {w ∈ {a, b}*, Na(w) mod 2 = 1}

I cannot solve this problem, if anyone can solve this problem. my problem is L = {w ∈ {a, b}*, Na(w) mod 2 = 1}
Mohammadreza Salehi
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(T/F) Given an NFA that has null/epsilon transitions, one can create another NFA that accepts the same language but has NO null-transitions

True or false and say why: Given an NFA that has null/epsilon transitions, one can create another NFA that accepts the same language but has NO null-transitions.
Collin
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Please help me covert the dfa to regular expression

i don't know how to use algorithm to covert this dfa to regular expression. Please help me.
cyshes21
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Desgin DFA that will accept strings having a's and b's divisible by 3?

DFA - DETERMINISTIC FINITE AUTOMATA for eg-abaabbbbb number of a's - 3 number of b's - 6 which are divisible by 3
Amogh Joshi
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How is it possible that the language a^n b^2n is regular if and only if it was finite such that 100 => n <= 0?

how is it possible that the language a^n b^2n is regular if and only if it was finite such that 100 => n <= 0? I know that a language in such a form of ( a^n b^n ) when n=>0 is not regular, since we need a temporary memory to keep track of the…
x200
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how this language is not recursive?

This question was asked at Gate 2009. I don't understand how it's not recursive? L = {Am Bm C An Bn | m, n ≥ 0} L' = {Ai Bj Ck | i, j, k ≥ 0} Why is language {L intersection L'} not recursive?
Anshika Agrawal
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Give a Regular Language L

Give a regular grammar for L= {a^n b^n : n<=100} I would do something like this : s---> A | empty string A---> aB| empty String b---> Ab but How do we keep count of the number in the grammar? meaning How does it know when there are more that 100…
Shutong Liu
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(T/F and explain) An NFA accepts the empty string if and only if its start state is a final state

Does an NFA accept an empty string if and only if its start state is a final state? Is this true? Please explain why. This question is related to Automata and NFAs and DFAs.
Collin
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Regular expression [ 1 ( 0 1* 0)* 1 ]* DFA

What are the conditions for the chain to be accepted by this regular expression?
Brandon Garcia
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