[Israel.pm] Regexp

[Mikhael Goikhman]

On 02 Jun 2005 11:05:05 +0300, Peter Gordon wrote:
> 
> Suppose I have the text "HarryMaryJaneHarryxMaryJane" and I want to find
> the longest duplicate match.
> 
> If I use /(.+).*?(\1)/
> it matches Harry, but the longest match is MaryJane. 
> 
> What is the best approach to this problem?

Without thinking too much on this problem, I would solve it like this:

	my $string = "HarryMaryJaneHarryxMaryJane";
	my $longest_substr = "";
	while (length $string) {
		$longest_substr = $1
			if $string =~ /(.+).*?\1/s
			&& length($1) > length($longest_substr);
		$string =~ s/^.//s;
	}
	print "$longest_substr\n";

And if you want to make it a bit more efficient, replace
	$string =~ /(.+).*?\1/s
with
	$string =~ s/^.*?(.+).*?\1/$&$`/s

Regards,
Mikhael.

-- 
perl -e 'print+chr(64+hex)for+split//,d9b815c07f9b8d1e'