Regular Expressions

Which language is accepted by the regular expression 0*(10*1)*0*10*

• {w | w has even number of 1’s}

• {w | w has odd number of 1’s}

• {w | w has even number of 0’s}

• {w | w has odd number of 0’s}

What is the regular expression for the language {w | w starts and ends with the same alphabet}?

• 0*(0 + 1)*0* + 1*(0 + 1)*1* + ϵ

• 01*0 + 10*1 + ϵ

• 0(0 + 1)*0 + 1(0 + 1)*1 + ϵ

• 0*1*0* + 1*0*1* + ϵ

The set of all strings over ∑ = {a,b} in which all strings having bbbb as substring is

• (a+b)* bbbb (a+b)*

• (a+b)* bb (a+b)*bb

• bbbb (a+b)

• bb (a+b)*

Write a Regular expression where the language contains set of strings containing even number of a's followed by odd number of b's.

Which of the following regular expressions denotes a language comprising of all possible strings over S = {a, b} of length n where n is a multiple of 3.

• (aaa + bbb)*

• ((a + b)(a + b)(a + b))*

For the alphabet S = {a, b}, give regular expression for the language of all strings that START OR END with ab.

• ab(a + b)*(a + b)*ab

• ab(a + b)* + (a + b)*ab

• (a + b)*ab(a + b)*

• ab(a + b)*ab

For the alphabet S = {a, b}, give regular expression for the language of all strings that CONTAIN the substring ab OR ba.

• (a + b)*ab(a + b)*

• (a + b)*ba(a + b)*

• (a + b)*(ab + ba)(a + b)*

• ab(a + b)*ba

For the alphabet S = {a, b}, give regular expression for the language of all strings containing EXACTLY two a’s.

• (a + b)*a(a + b)*a(a + b)*

• b*ab*ab*

For the alphabet S = {a, b}, give regular expression for the language of all strings containing AT LEAST two a’s.

• (a + b)*a(a + b)*a(a + b)*

• b*ab*ab*

Which of the following regular expressions denotes a language comprising of all possible strings over S = {a, b} that START AND END with aa.

• (aa)*

• aa(a + b)*aa + aa + aaa