# Questions tagged [dfa]

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### Error in Robson's proof about separating strings?

One of my students discovered a possible mistake in Robson's classic paper Separating strings with small automata. The issue is in the proof of Theorem 1, giving the simpler bound $O(\sqrt{n\log n})$. ...
38 views

### How the correctness of this construction can be proved? [closed]

We are using Myhill-Nerode Theorem algorithm and we want to prove that this algorithm gives us the minimized DFA. So let $B$ be the minimized DFA obtained by applying the algorithm to the DFA $A$. We ...
62 views

### Updating (minimal) DFA incrementally

Is there algorithm to incrementally update (minimal) DFA? Namely, having relatively large minimized DFA I want to update it incrementally using union and sudtraction with other (relatively small, ...
1 vote
106 views

### Real life application of two-way DFA

I am currently studying two-way DFA and I couldn't find and research anything on its real-life applications if there are any. I am very unsure where it could be used and any ideas would be great. tyia
227 views

### Is DFA language inclusion decidable in quasi-linear time? [duplicate]

Given two DFAs $A_1$ and $A_2$, we want to decide whether $\mathcal{L}(A_1) \subseteq \mathcal{L}(A_2)$. Of course, one can compute whether $\mathcal{L}(A_1) \cap \mathcal{L}(A_2) = \mathcal{L}(A_1)$. ...
117 views

### What is the Simplest type of automaton that can simulate all DFAs?

During recent research in a somewhat unrelated field (Spin Physics), I stumbled across a subclass of regular languages. The context of the research poses the question what the minimal power of the ...
108 views

### I have to make a dfa over the alphabet Σ = { 0, 1, 2 } of strings that end with the same digit twice; e.g., strings that end in 00, 11, 22 [closed]

hi can you please go over my dfa for this and tell me if its correct??
205 views

### Random Cerny Conjecture

For simplicity, all DFAs will be using the binary alphabet $\{0,1\}$. Let $M$ be a synchronizable DFA. We let $p(M,n)$ be the probability that a random $x\in \{0,1\}^n$ will synchronize $M$. We define ...
406 views

### Bounds on this Strategy for Separating Words

Question Given binary string $z \in \{0,1\}^n$, let $f(z)$ be the smallest integer $k$ such that there exists a DFA with $k$ states, such that reading $z$ from a specific starting state, we end at a ...
771 views

190 views

### Separating words and graph isomorphism

I wonder if there are any known implications of Babai's recent quasi-polynomial time algorithm for Graph Isomorphism to separating words by DFA's. In both cases the ultimate goal is to differentiate ...
284 views

### Shortest string in the intersection of regular languages

Inspired by https://codegolf.stackexchange.com/questions/53310/shortest-universal-maze-exit-string Each of the 138,172 valid mazes can be represented as a DFA with 9 states (including starting and ...
290 views

### Is Bayes optimal RL of a finite set of DFAs feasible?

Let $Q$ be a finite set of states, $\Sigma$ a finite alphabet, $q_0\in Q$ the start state and $F\subseteq Q$ the set of accepting sets. Let $\{\delta_k:Q\times\Sigma\rightarrow Q\}_{k=1}^n$ be a set ...
110 views

### When designing a DFA, am I allowed to design two separate Machines and perform an Intersection on them? [closed]

I am trying to design a DFA s.t. The set of strings in x ∈ {0, 1}∗ such that the number of zeros is a multiple of 3 and the number of one's is even. My idea was to create two Machines M1 = (Q1, Σ, δ1,...
465 views

### NFA to 2DFA: what are the upper and lower bounds?

Suppose that one has an NFA (from, say, a regular expression). What is the state complexity of turning it into a 2DFA?
78 views

### Non equivalent states shortest word [closed]

My textbook contains a theorem that if you have a DFA and two states that are not-equivalent, then there is a differentiating word that has length smaller than amount of states in that DFA. How do we ...
74 views

### Structural property of DFAs/NFAs accepting LTL-definable languages

I consider LTL on finite words. In this context, there are a couple of nice equivalence results for a language L: L is LTL-...
1k views

### NFA to DFA Powerset Construction : A Partial determinization algorithm with trade-off between running time and size for the resulting automata?

Given a NFA $N$ and its equivalent DFA $D$ resulting from the total determinization of $N$ (using powerset construction, for example), the following properties hold for $N$, $D$ and for any word $w$ : ...
213 views

1 vote
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### What is the relation/difference between axiomatic and denotational semantics one one side, and the data flow analysis(DFA) on the other sied?

I am supposed to write a small paper about DFA in OOP for a CS class in theory. But I am required to connect that (DFA) to axiomatic and denotational semantics! I read few resources about axiomatic/...
148 views

### When does automaton stay unchanged after string homomorphism?

Suppose we have a string homomorphism $\varphi: \Sigma \rightarrow \Sigma^*$. Consider the languages in $\varphi(\Sigma^*)$ whose letters are elements of $\varphi(\Sigma)$, so here I do not want to ...
1k views

### Finding the smallest DFA that separates two words without using brute force search?

Given two strings x and y, I want to build a minimum size DFA that accepts x and rejects y. One way to do this is brute force search. You enumerate DFA's starting with the smallest. You try each ...
1k views

### DFA intersection algorithm for special cases

I'm interested in efficient algorithms for DFA intersection for special cases. Namely, when the DFAs to intersect obey a certain structure and/or operates on limited alphabet. Is there any source ... 2k views

### How to XOR automata? [closed]

Say we have 3 DFAs. We know how to OR, AND, or NOT them. But how does one XOR them? There is not one single mention of this online. x XOR y XOR z = ((x|y)(~x|y)|z) (~((x|y)(~x|y))|z). This is way too ...
499 views

### Separating words with random DFAs

One of the interesting open problems about DFAs listed in Are there any open problems left about DFAs? is the size of a DFA required to separate two strings of length $n$. I am curious if there any ...
333 views

### Composition of regular expressions with lookahead into DFAs

Let's say we have a regular expression ("a" | "b"(~!"b"))*, written in Perl or other similar languages that support lookahead, which should match a list of a and b's where b's are not followed by b's. ...
9k views

### Are there any open problems left about DFAs?

After studying deterministic finite state automata (DFA) in undergrad, I felt they are extremely well understood. My question is whether there is something we still don't understand about them. I don'...
961 views

### Languages recognized by polynomial-size DFAs

For a fixed finite alphabet $\Sigma$, a formal language $L$ over $\Sigma$ is regular if there exists a deterministic finite automaton (DFA) over $\Sigma$ which accepts exactly $L$. I am interested in ...
260 views

### Are there any books containing collections of automata problems?

You can find specialized books consisting entirely or problems from particular math domains (e.g. linear algebra, polynomials, combinatorics), but I've yet to find such a book for automata of any kind....
713 views

### What are good conferences for algorithms about finite automata?

I am writing a research paper, which describes some properties about finite automata. It also provides a couple of algorithms that can measure some aspects of the properties. Could you point out some ...
202 views

### Exploring a DFA, with no feedback

Let $M=(\Sigma,S,s_0,\delta)$ be an (unknown) deterministic finite-state automaton (DFA), with alphabet $\Sigma$, statespace $S$, start state $s_0 \in S$, and transition relation $\delta$. I want to ...
234 views

### Finding self-similar homomorphisms of a FSM transducer

Consider a special case of homomorphisms of FSM transducers (or "generalized sequential machines" in ). Let $F$ be a transducer accepting a language $L$, and let $h(x)$ be a homomorphism function ...
663 views

### How to minimize a FSM transducer?

In contrast to FSM minimization which is well studied with various algorithms, theorems and has many practical applications, I'm looking for any nontrivial insight, analysis and references to the ...
3k views

### Algorithm for converting very large NFA to DFA

I have really large Non-deterministic finite automaton and I need to convert it to the DFA. By large I mean 40 000+ states. So far I have done some experiments and programmed the default algorithm ...
160 views

Consider the deterministic (resp. non-deterministic) one-way finite automaton that is defined in the usual way except that it has k heads and in each step can decide which head to move. (It is allowed ...
2k views

### minimizing size of regular expression for finite sets

It is known that minimizing the size of a regular expression is PSPACE-complete even if we have a DFA as the language's specification. What are the results if the language is finite? One can ...
400 views

### Multi-language DFA minimisation

I'm interested in a slight generalisation of DFA. As usual we have state-set $Q$, finite alphabet $\Sigma$, a $\Sigma^*$-action defined on $Q$ by $\delta : Q\times\Sigma\rightarrow Q$, and initial ...