I'm trying to construct a regular expression for the language of binary strings in which every 00 must have at least two 1s before it.
I realize this can be done with lookbehinds using the following regex:
^(?:(?<=11)00(?!0)|(?<=1)0|1+)+$ , however I am now trying to construct a regular expression in the sense of formal language theory.
I currently have
(0+ε)(11*0)*1* ), which gives me the language of binary strings without consecutive 0s, but am not quite sure how to get the 'conditional' part in without actually using a conditional.