Regex to match a string like ababba etc
Based on @Michails great answer - I played and tried to get it below 12 characters. With 10 (demo)
Still I wonder, if it works fine. It will be definetly faster with start anchor (demo).
^From the beginning :
(?=aba|a$)Will start by aba to make sure it starts with one b (no match, just a check)
a(b+)An a followed by several b (capture the number of b)
(?=a\1ba)this abbb must be followed by a, one more b, then a
|a$except for the last one of course, which is simply followed by the last a
*repeat this pattern of "ab+ with one more b each time"
a$match the final a
Test it on https://regex101.com/r/J5rXH9/3
You would try this: