Date: 11 Jul 2001 20:15:47 GMT
From: ctcgag@hotmail.com
Subject: Re: Data structures question.
Message-Id: <20010711161546.494$e0@newsreader.com>

garry_short@hotmail.com (Garry) wrote:
> Hello.
>
> I'm trying to work out one of two things, assuming either is possible.

Of course they are.

> The first option is a 2d array, 9 columns wide by 10k+ rows deep.

OK, I'll assume that's @x[$col][$row]

> Is
> it possible to sort the array by the nth row?

I'll assume you mean $nth column, just because that's the way I think of
it, and I'm pretty sure that's what you meant anyway.

> If so, could anyone give
> me some pointers on how to do it?

assuming that you want to sort text (rather than numbers), here's a way:

@index = sort {  $x[$nth][$a] cmp $x[$nth][$b] } (0..$#x);
@sortedx= @x(@index);

You can chain together to get rid of the @index variable if you want.
It's there for pedagogical poirposes only.

> Better still, can I sort that array by multiple columns, as per Excel?

@index = sort {  $x[$nth1][$a] cmp $x[$nth1][$b]
                              ||
                 $x[$nth2][$a] cmp $x[$nth2][$b]
                              ||
                 $x[$nth3][$a] cmp $x[$nth3][$b]  } (0..$#x);

Here, you only look at the $nth3 column if both $nth2 and $nth1 have
already compared equal.


> If so, does anyone what's the maximum number of columns I can sort by?

Depends on where/when your computer pukes.

Xho


> --
>
> Assuming that's not possible, has anyone got any suggestions on
> implementing the following data structure :
>
> array of (unique SRC_IP,
>   array of (unique SRC_PORT,
>     array of (unique DEST_IP,
>       array of (unique DEST_PORT,
>         array of (unique PROTOCOL,
>           array of (unique DATE,
>             array of (unique TIME,
>               array of (TYPE, CODE)
>             )
>           )
>         )
>       )
>     )
>   )
> )

I would suggest not implementing it.  Or at least implementing it as
chained hashes rather than chained arrays.


Xho

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