Question

How many distinct strings are in the language of the regular expression:
(0+1+ϵ)(0+1+ϵ)(0+1+ϵ)(0+1+ϵ)

Answer 1

what does '+' means? one or more element?

Answer 2

I think the answer is 31 .. as we have 2 digits that may concatenate to form (4 or 3 or 2 or 1 or 0) digits number so the possible combinations are the summation all possibilities
2^4 + 2^3 + 2^2 + 2^1 + 2^0

Answer 3

if '+' means one or more element then it can be infinite else I don't know what it means because it's usually means one or more element