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Re^2: Finding repeat sequences.

by BrowserUk (Pope)
on Jun 18, 2013 at 19:59 UTC ( #1039642=note: print w/ replies, xml ) Need Help??


in reply to Re: Finding repeat sequences.
in thread Finding repeat sequences.

They are kind of hard to come up with, but okay.

Given the rep 'aaaabaaaaba' and a string containing one whole and one partial rep 'aaaabaaaabaaaaabaaaab'

$s = 'aaaabaaaabaaaaabaaaab';; $s =~ m[(.+).*\1] and print $1;; aaaabaaaab

Which isn't correct because:

aaaabaaaabaaaaabaaaab aaaabaaaab aaaabaaaab 1 ^2

You can fix that by removing the redundant .* per LanX's version: m[(.+)\1] but then you get:

$s = 'aaaabaaaabaaaaabaaaab';; $s =~ m[(.+)\1] and print $1;; aaaab

Which isn't right:

aaaabaaaabaaaaabaaaab aaaabaaaab aaaabaaaab 1 2 ^3 4

I realise that this is a 'cheat' as there in no complete repetition to find, but it is one possible scenario.

Given the string will always consist of 1 or more repetitions of the substring, whatever partial substring (if any) is at the end of the string should match the same number of characters at the start of the string. That's the bit I'm having trouble wrapping my head around.


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