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From: bjaspan@ATHENA.MIT.EDU (Barr3y Jaspan)
Newsgroups: comp.lang.perl
Subject: Re: How to sort on right most column
Message-ID: <1991May15.182131.20425@uvaarpa.Virginia.EDU>
Date: 15 May 91 18:21:31 GMT
Sender: mmdf@uvaarpa.Virginia.EDU (Uvaarpa Mail System)
Reply-To: bjaspan@ATHENA.MIT.EDU
Organization: The Internet
Lines: 42


|> I have the following data in this format - I want to sort it on the
|> right most column.
|> 
|>   0    1   2                              3                     4
|> 
|>   a    b   c                              c                     e
|> 
|>  FOO  BAR ACE CORPORATION                SUNNYVALE              2.00
|>  FOO  BAR ACER COMPUTED COMPANY          MILPITAS              20.00

(Introduction: I'm not sure what the first two lines ("0  1   2 ...")
are for, so I'm ignoring them. :-)

Well, since you know the sort key is the last number on each line, you
could do something like this (untested):

while (<>) {
	/([\d.]+)$/;
	$lines{$1} = $_;
}

for (sort numerically keys %lines) {
	print $lines{$_};
}

sub numerically {
	$a <=> $b;
}

The idea is to use the number at the end of a line as a key in an
associative array, storing each entire line of text keyed on its final
number.  (You could do this more "efficiently" with a normal array if
you knew (1) that all your numbers were integers and (2) that all the
numbers were "small".)  Then you just sort the keys and print the
respective lines of text, in order.

(You could also split the entire line on whitespace and use the last
element in the returned array as your key; I suspect (but I'm not
sure) the first way is faster.)

Barr3y Jaspan, bjaspan@mit.edu