smitz has asked for the wisdom of the Perl Monks concerning the following question:

Noble Monks:
I've just completed my 1st real program that actually achieves something, and damn it feels good. One part of this script, though, contains an array of arrays, like so:

$array[$i] = [x, y, z];

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This array needs to be sorted in order to find the $i with the smallest z value. Not too hard, and I did myself.
The problem lies with this website. Since coming here I have seen code so short, efficient, beautifull, etc. that I get quite a minority complex. When I look at the way I sort my array, I just dont like it. Its, well, amateurish. I know this is a simple problem which I have solved, but I would like to see how a real monk would do it.

Thanks for your time,
SMiTZ

Replies are listed 'Best First'.
Re: Array sort - kind of...
by wog (Curate) on Feb 04, 2002 at 00:57 UTC

    @array = sort { $a->[2] <=> $b->[2] } @array

    But, you say you want to find the $i with the smallest z value. It's best to _not_ sort for that: 

    my $min_i = 0;
foreach my $i (1..$#array) {
  $min_i = $i if $array[$i]->[2] < $array[$min_i]->[2];
}

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    (update: Oops. Forgot the ->[2].)

    This should be signifigantly faster, especially when @array gets large...

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      This isn't relevant at all for the issue, but I have a question: Why do you choose to have $i over $_? There is a slight performance improvement when the loop is entered, but still...
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        True, he could have it written it in such a way to minimize a bunch of the minor overheads of the loop construct.

        Thus 

        my $min_i = 0;
foreach my $i (1..$#array) {
  $min_i = $i if $array[$i]->[2] < $array[$min_i]->[2];
}

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        becomes 
        my $index=0;
$array[$_][2]<$array[$index][2] && ($index=$_)
   foreach 1..$#array;

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        But I'm so sure its easier to understand...

        ;-)

        Yves / DeMerphq
        --
        When to use Prototypes?

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        I find it clearer, since smitz referred to $i as the index to the array in the question and since $i, $j, etc. make me think "this is a counter variable" when I see them.
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