# Questions tagged [finite-automata]

Questions about finite automata, an elementary automaton model with finite memory. It is equivalent to regular languages and the basis for many more complex models.

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### Copy operation in under 9 states?

There is a long row of cells. Each cell contains 0 or 1. A machine is positioned immediately to the right of a series of uninterrupted 1’s followed by an uninterrupted series of 0’s. In the following ...
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### Minimal DFA for $1\Sigma^*0$

What is the minimum number of states required in any DFA to accept the regular language $L$ over $\Sigma=\{0,1\}$ which accepts those strings that start with 1 and end with 0?
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### Over the alphabet {a,b,c,d}, how would i construct a NFA that only accepts strings that end with a letter that is already part of the string?

I've been trying to create a NFA that accepts strings that end with a letter that exists in the string. For example abcdb, cbdd, acac etc. while strings like abc aacd etc are not accepted since the ...
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### Use DFA minimization on LR(1) states

I have recently started reading more about context-free parsing techniques, in particular LR parsing. As I have read, LR state transition graph (or table(s)) used for finding handles in sentential ...
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### Determine the number of reachable states in a subset construction?

Is there a polynomial time algorithm to determine the number of reachable states in the subset construction of a NFA to a DFA without having to construct the entire DFA?
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### Is $L = \{ w : \#_a(w) = \#_b(w) \}$ regular?

Is $L = \{ w : \#_a(w) = \#_b(w) \}$ regular? I do not think it is. I recently posted a question and from there I was thinking if this language is regular. If we assume on the contrary, then there ...
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### Conversion of $\epsilon$-NFA to a DFA

So, I was watching a video about the conversion of $\epsilon$-NFA to a DFA. In the resulted DFA, she didn't write the state 4 in any successor set of the sets containing the state 3, and her ...
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### Is the set of strings with equal number of 010’s and 101’s regular?

Consider the language $$L = \{ w\in \{ 0, 1\}^*: \#_{010}(w) = \#_{101}(w) \}$$ Is $L$ is regular? If it is not regular, can we prove that using the pumping lemma (only with pumping down)?
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### DFA to accept a String containing even number of both A and B, but rejects empty String

I want to draw a DFA to accept a String containing even number of both A and B, but rejects the empty String(ε) I have already drawn the DFA which accepts the above language, without rejecting the ...
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### How do i prove this language is regular? [duplicate]

I have this language {0+1+0+} and i need to prove it is regular,i had the idea to use the closure properties but i can find any regular languages to unify perhaps.Any ideas?
I am unsure what it means for a grammar to be $X$. More specifically, what it means for a grammar to be LR(0). For part of an assignment I had to form the DFA for a grammar, which I had no issues with....