July2016 cs Q31

31The number of strings of length 4 that are generated by the regular expression (0|∈)1+2* (3|∈), where | is an alternation character, {+, *} are quantification characters, and ∈ is the null string, is :

Option : D
Explanation :
Regular expression (0|∈)1+2* (3|∈) 0122, 0123, 1123, 0112, 0113, 1113, 0111, 1222, 1123, 1111, 1223, 1112; Total 12 strings of lenghth 4 are possible. So, option (D) is correct.

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