Given a string of arbitrary (long) length that is known to comprise of a number of repetitions of an unknown length substring, (thought the last repetition my be incomplete), how to find that repeat sequence?

Eg. Given 'abcdabcdabcdabcdab' find 'abcd'.

Complications:

  1. The first (shortest) repetition may not constitute the full repetition.

    Eg. In 'abcdabcdabceabcdabcdabceab'; 'abcd' is a false rep; the required rep is 'abcdabcdabce';

  2. As mentioned, the last part of the string may be an incomplete repetition.

    The number of characters 'ignored' at the end of the string should be less than the length of the rep. Is is possible to code that into a regex? I guess it could just be checked afterwards.

I'm assuming that a regex solution would be possible, but I cannot wrap my brain around it today?

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In reply to Finding repeat sequences. by BrowserUk

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