GATE CSE 1987 | Question: 10d

Question

Give a regular expression over the alphabet $\{0, 1\}$ to denote the set of proper non-null substrings of the string $0110$.

Comments

what is the proper meaning of non null sub string ?

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is 0110 a substring of 0110 or not?

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0110 is not a proper substring of 0110 but it is a substring. So eps and 0110 are excluded.

Answer 1

I think regular expression would be:(0+1+01+10+11+011+110)

Comments

Please try to add something extra in your answer because this solution is already given.

Answer 2

Since we have to get only non NULL substrings, hence ∈ should bot be present.

(0 + 1) ( 0 + 1 + ∈) ( 0 + 1 + ∈)

Please correct me if i am wrong

Comments

000 is produced by your RE, which isn't a substring.