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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".

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Regex | Containing "bbb"

I'm trying to create a Regex with chars 'a' and 'b'. The only rule is that the regex must contain the word 'bbb' somewhere. These are possible: aabbbaaaaaababa, abbba, bbb, aabbbaa, abbabbba, ... These are not possible: abba, a, abb, bba,…
silberfuchz
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PDA question > need help

i have a task to construct the PDA which recognizes the language A= {a^m b^n | m > n} with ∑ = {a, b}.. i'm a bit confused how to do it.. can you guys help me to solve this question? thanks
tan keng
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Gradually transitioning FSM

It is given that a particular object can have two states at any point in time and that the object transitions from one state to another gradually. I am modeling the state-graph to capture all the possible states the object can have and their…
Mahesh
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Build grammar to the language

L = {a^i b^j c^k | not(i=j=k)} Hint : describe L as a union of other languages I have been trying to do this for like a week now and just can't. Can anyone help me understand? Edit : Is it right to say : (i≠j or j≠k) or (i≠j and j≠k and i≠k)
Angel Adir
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What is the typical alphabet size of Finite State Machines?

Not quite sure if this is the correct forum, but it was suggested at Theoretical Computer Science that I move it here... What is the typical alphabet size of Finite State Machines? I am currently busy implementing a high-performance FA library and…
Nico Huysamen
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Problem with Automata simple conditional statements in C#

I am trying to build an automata, I've dried run several times and there seems no problem in the code but still I am not getting the desired result i.e "CurrentState" which should be X3 Input I am giving is as follow string[] input = new string[4] {…
Sunny
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REGEX L(r) = {a^n b^m : n + m is even}, r =?

So I did a problem earlier that said: L(r) = {w in {a,b}* : w contains at least 2 a's} For that one I said {a^2n , b} because that guarantees a string like aab or aabaab etc. Not sure how to approach the one I posted about in the title. Possibly a…
solnay
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What does it mean to pass the machine and it's description as the input in the halting problem?

In the proof of the halting problem, why do we have to pass the machine and its description as an input? For example, I could have passed the description of the machine and some other input(not the machine itself) and still the proof by…
sayantan dasgupta
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How to understand DFA (Finite Automata)?

Indicate the state that the DFA will end in after processing each of the following input strings. Note: the input labeled "The empty string" is literally the empty string—a string with no letters in it—not the letters 'T', 'h', 'e', ' ', 'e', and…
user3222184
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What if all states are accepted in Minimizing Deterministic Finite Automata with Hop-croft Algorithm?

Here we have a DFA like this: Is this already a minimized DFA or should we minimize it using Hopcroft algorithm by grouping all accepted states in one class and output:
BobHU
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Can Countable string is Countable always?

Why some sets are countable and some are not countable? Say regular set are countable but how (0+1)* will be countable? It is an infinite string, then how it could be a countable set? How the set of all non-decreasing functions from N to N are…
Srestha1
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NFA for base m no divisible by n

I was given an exercise to find DFA for base m no divisible by m. I found out how to do this, thanks to this link, but then I wondered how would we approach this exercise if it was to create an NFA and then convert it to DFA using subset…
Nisha
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Why Doesn't This NFA Accept Empty String?

We were given the definition of a NFA and told to construct an equivalent DFA using the conversion process. I had no issues, however, our professor kept telling us after the assignment that original NFA didn't accept the empty string. I'm a bit…
JosephTLyons
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How to construct a PDA for n(a) is less than or equal to 2n(b)

So here is where I am stuck, I have to construct a PDA that would accept words from {a,b}* with the condition n(a) is less than or equal to 2n(b)
Sindhu Bharathi
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Can any tell me the regular expression for the given language?

all strings which contains even number of 0s or even number of 1s. Here I am asking about 'or' not 'and'. I have come up with this: (1*01*0)*|(0*10*1)* so far...but this seems wrong to me cause when you draw DFA for the above language you can even…
Ronit Sharma
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