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### Simple regular expression problem [duplicate]

new to automata theory and this is quite difficult for me so I'd appreciate a hint in the right direction if possible. We want to find a regular expression for the language $L$ over $\Sigma = {a,b,c}$...
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### Regular expression for set of strings with no two consecutive 1's? [duplicate]

I'm having trouble figuring out a regular expression over the alphabet {0,1} that contains all strings with no TWO consecutive 1's. I'm also wondering if there is a pattern that could be extended to ...
158 views

### Regular expressions for words avoiding aaa,bbb,ccc [duplicate]

I need to write a regular expression for all words over $\{a,b,c\}$ not containing $aaa$, $bbb$ or $ccc$. Will appreciate any help. Note: this is not homework.
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### Give regular expression on language [duplicate]

What is a regular expression for $L_1=\{a^{2n} b^{3m+1} \mid n \geq 1, m \geq 0\}$?
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### How to write a regular expression that excludes certain strings? [duplicate]

It's a homework problem. Assume $\Sigma = \{a ,b\}$, I am asked to construct a regular expression that does not have both the substrings bba and abb. My idea was: construct a regex that matches ...
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### How to write regular expression [duplicate]

The set of all strings over {0,1} such that every block of 4 consecutive symbol contain at least two 0's Can you guys tell me what is the correct answer for this ?
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### Regular expressions for some languages [duplicate]

Set of strings over $\{0,1\}$ having at least two occurrence of the substring 00. $\{a^n b^m : n ≥ 4, m ≥ 3\}$. Set of strings over the alphabet $\{a,b,c\}$ containing at least one $a$ and one $b$.
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### How to convert finite automata to regular expressions?

Converting regular expressions into (minimal) NFA that accept the same language is easy with standard algorithms, e.g. Thompson's algorithm. The other direction seems to be more tedious, though, and ...
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### How to prove a language is regular?

There are many methods to prove that a language is not regular, but what do I need to do to prove that some language is regular? For instance, if I am given that $L$ is regular, how can I prove that ...
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### Write a regular expression - Contains an equal number of 01 and 10 subtrings

I'm trying to write a regular expression for the language $L\subseteq\{0,1\}^*$ of strings that begin with $0$ and contain an equal number of occurrences of the substrings $01$ and $10$. ...
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### DFA for Strings with third symbol from RHS as 1

How can we make a DFA for given condition in title from alphabets {0,1} (binary). What can be the regular expression for this? My calculated expression is (a+b)*a(a+b)(a+b) , please correct me if i'...
What is a regular expression or finite automaton that will accept words in the alphabet $\{a,b,c \}$ where each letter appears at least once? Acceptable words: $abc, cba, cbcbcba, abbbcaabb$ ...
I'm trying to write a regular expression over the alphabet $\{a, b\}$ for the language in which every $b$ is preceded and followed by an even number of $a$'s. I think the regular expression should ...