Question

regular expression for " set of all strings over {a,b} in which there are at least two occurrences of b between any two occurrences of a ".

Answer 1

Here is my try:

$b^{*} + b^{*}(abb^{+})^{*}ab^{*}$

Comments

yes...b,bb,bb....can be generated...clear ur doubt

assume R.E ====>   A+B  means we can either take A or B at a time but not both...for generating any string..

and     A^*  +  B*/////means  we can either take A any no.of time  or B any no.of time but not both...for generating any string..

and   ( A  +  B)*///brackets are important..means  we can either take A any no.of time  or B any no.of time or BOTH...for generating any string..

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if we write (a,b)^+ or (aUb)^+ or (a+b)^+ does they all mean same ?

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yes..