Finding a group match part of another group in a regex

Question

I was just wondering how to match a group which has characters already in another group.

If we take this string for example: "aba" and want to match every group of (ab) or (ba).

Obviously (ab|ba) would work, my only problem with that is it only catches one group which is aba but i also want to capture aba, do I have to use a more complex regex for this case?

Answer 1

You can easily achieve this using this regex

(?=(ab|ba))

It will match all the occurrences of both 'ba' and 'ab' even the overlap ones.