Re: counting overlapping patterns


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Re: counting overlapping patterns

by Limbic~Region (Chancellor)

on Feb 18, 2005 at 20:30 UTC ( [id://432504]=note: print w/replies, xml )

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in reply to counting overlapping patterns

Anonymous Monk,
Here is some code that covers your example, but it admittedly only works on fixed strings since it doesn't use regular expressions at all.

#!/usr/bin/perl
use strict;
use warnings;

print str_count('AAAA', 'AA'), "\n";

sub str_count {
    my ($str, $pat) = @_;
    my $tot;
    for ( 0 .. length( $str ) - length( $pat ) ) {
        $tot++ if index($str, $pat, $_) - $_ == 0;;
    }
    return $tot;
}
[download]

Cheers - L~R

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Re^2: counting overlapping patterns
by Limbic~Region (Chancellor) on Feb 19, 2005 at 16:14 UTC

bobf

nothingmuch

nothinmuch

#!/usr/bin/perl
use strict;
use warnings;

print str_count('ABAABAAAA', 'AA'), "\n";

sub str_count {
    my ($str, $pat) = @_;
    my %substr;
    my ($p_len, $s_len) = (length $pat, length $str);

    my $template = ("A$p_len" . 'X' . ($p_len - 1)) x ($s_len - $p_len
+ + 1);
    $substr{$_}++ for unpack $template, $str;
    return $substr{$pat};
}
[download]

Cheers - L~R

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