here a regex solution which works for the shortest possible tail of length k
DB<128> $str=~/^((.+?).*)\2$/; $rest=$1, $tail=$2
=> ("abcdabcdabceabcdabcdabce", "ab")
DB<129> $rest =~ /^(.+?)\1*$/; $1
needs to be extended for longer possible tails.
But taking the dimensions of your data I doubt that regexes are appropriate.
You could test all $patterns which repeat at least once (or x times) and calculate $k = $m % $l with $m =length ($str), and check if $str starts and ends with the same substring $tail of length $k and then check if the pattern continues repeating.
Or start eliminating all possible $tails and check if $l of a repeating pattern is a divisor of the $rest.
Had no time to check all the other posted solutions and don't wanna reinvent the wheel, so I better stop here! =)
( addicted to the Perl Programming Language)
Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
Read Where should I post X? if you're not absolutely sure you're posting in the right place.
Please read these before you post! —
Posts may use any of the Perl Monks Approved HTML tags:
You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
- a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
Link using PerlMonks shortcuts! What shortcuts can I use for linking?
See Writeup Formatting Tips and other pages linked from there for more info.
| & || & |
| < || < |
| > || > |
| [ || [ |
| ] || ] ||