Hi shamat,

Wow, this question brings me back to what was - as far as I can remember - probably the first time I visited PerlMonks :-) Specifically, it was Re: How do I do a natural sort on an array?, that snippet was very helpful to me over the years. So I revived it and applied it to your code:

use warnings;
use strict;

my @matrix = (
    ["A12a1", "img5", "x456", "y456"],
    ["A1a2",  "img2", "x123", "y456"],
    ["A1a1",  "img1", "x123", "y123"],
    ["A10a1", "img4", "x456", "y123"],
    ["A1a12", "img3", "x456", "y789"],
);

my @sorted = sort natsort @matrix;
use Data::Dump 'pp';
print pp \@sorted;

sub natsort {
    # sort by first column (note the dereferencing)
    my @a = split /(\d+)/, $a->[0];
    my @b = split /(\d+)/, $b->[0];
    my ($A,$B);
    while (defined($A = shift @a) and defined($B = shift @b)) {
        my $res = ($A =~ /\d/) ? $A <=> $B : $A cmp $B;
        return $res if $res;
    }
    return defined $A ? -1 : 1;
}

__END__

[
  ["A1a1", "img1", "x123", "y123"],
  ["A1a2", "img2", "x123", "y456"],
  ["A1a12", "img3", "x456", "y789"],
  ["A10a1", "img4", "x456", "y123"],
  ["A12a1", "img5", "x456", "y456"],
]

[download]

The way this works is by breaking each string up into its digits and non-digits, for example "A12a1" becomes ("A", 12, "a", 1), and then each element is compared individually. This does assume that the two strings being compared follow the same digit/non-digit pattern. Also, it's not a particularly efficient sort method, as it does a lot of work for each comparison. But it was just a walk down memory lane anyway :-)

Of course, there are also modules to do the hard work, just one example is Sort::Key::Natural.

By the way, I think you've got a mistake in your test data, you overwrite $matrix[1], that's why I've initialized the data as I showed.

Hope this helps,
-- Hauke D

In reply to Re: natural sort on array of arrays by haukex
in thread natural sort on array of arrays by shamat

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