Give a regular expression for each of the subsequent languages by performing a direct construction.
Part 1: The set of binary strings not containing consecutive 1's.
Part 2: The set of binary strings containing exactly one instance of 11 somewhere inside.
Part 3: The set of binary strings with at most one pair of consecutive 1's--i.e. if 11 is present, it can occur exactly once.
This one is complex and I don't know how to do it