How would you come up intuitively with a complement of the language expressed by the following regular expression: $(a + b)^*aba$?
Not intuitively, I would convert it to DFA, then get the complement out of the DFA, then convert the result to a regular expression through state elimination for example.
If I try to come up with an intuitive complement, I would say that it's $(a+b)^*abb$, but I can't verify.