TOC Sample Practice

Question

Choose the correct statement for the following regular expression over the symbols 0 & 1.
0(0+1)*0 + 1(0+1)*1
(a) To represent all strings over 0’s and 1’s
(b) To represent all strings which start with 0’s and end with 1’s
(c) To represent all strings which start and end with same symbol
(d) To represent all strings that starts and ends with 1’s

Comments

c is the option which is in the form of  WXWR where W,X belongs to (0+1)+

Answer 1

option C is correct.

it represents all strings which start and end with same symbol

Comments

why not B? it starts with 0 and ends with 1 as there is + sign dont we have to select from right side of + also?
+ 1(0+1)*1
if putting E then we get 11
so 00 from left side and 11 frim right side?

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'+' means either one of side you have to consider not both.

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confused!! :)

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Why option B is not,
Because there is '+' sign between two terms.
so either you choose 0(0+1)*0 or 1(0+1)*1
so it never makes any string starting with 0 and ending with 1.
because when you start with "0" you have chosen 1st term so it must end with "0" only.
same applies when you start with "1".
Hope you got it :)

Answer 2

Option C is correct!