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sorting a list with primary and secondery key

yaniv_av
Novice

Oct 31, 2002, 2:23 PM

Post #1 of 5 (395 views)

sorting a list with primary and secondery key	Can't Post

I have a file with a lot of records with 2 filelds each (line by line).
example:
yaniv : 12
asaf : 44
lui : 09
yaniv : 33
...

I want to sort the file with column 1 as the primary key and column 2 as the secondary key.
How can I do this efficiently ?
(I'm using perl under windows so I can't use the unix-sort-function that working great ...)

jryan
User

Oct 31, 2002, 6:08 PM

Post #2 of 5 (387 views)

Re: [yaniv_av] sorting a list with primary and secondery key [In reply to]	Can't Post

Code

 
sort { 
    (split /: /,$a)[0] ne  (split /: /,$b)[0] ? 
    (split /: /,$a)[1] <=> (split /: /,$b)[1] : 
    $a cmp $b 
} @records;

(This post was edited by jryan on Oct 31, 2002, 10:52 PM)

jryan
User

Oct 31, 2002, 6:12 PM

Post #3 of 5 (388 views)

Re: [jryan] sorting a list with primary and secondery key [In reply to]	Can't Post

On second thought, this will be more efficient:

Code

sort { 
  substr($a,0,rindex($a,":")) ne substr($b,0,rindex($a,":")) ? 
        substr($a,rindex($a,":")+1) 
    <=> substr($b,rindex($b,":")+1) : 
    $a cmp $b 
} @records;

(This post was edited by jryan on Nov 4, 2002, 2:29 PM)

Paul
Enthusiast

Nov 1, 2002, 2:29 AM

Post #4 of 5 (375 views)

Re: [jryan] sorting a list with primary and secondery key [In reply to]	Can't Post

....and you should use lc() incase there are case differences with your cmp comparison.

davorg
Thaumaturge / Moderator

Nov 3, 2002, 1:00 AM

Post #5 of 5 (364 views)

Re: [yaniv_av] sorting a list with primary and secondery key [In reply to]	Can't Post

The obvious approach is something like this:

Code

!/usr/bin/perl 
 
use strict; 
use warnings; 
 
my @data = <DATA>; 
chomp @data; 
 
@data = sort { 
  my @A = split /: /, $a; 
  my @B = split /: /, $b; 
 
  return $A[0] cmp $B[0] or $A[1] <=> $B[1]; 
} @data; 
 
print map { "$_\n" } @data; 
 
__END__ 
yaniv : 12 
asaf : 44 
lui : 09 
yaniv : 33

but with a large amount of data that might get a bit inefficient so you should probably consider some kind od Schwartzian Transform.

Code

#!/usr/bin/perl 
 
use strict; 
use warnings; 
 
my @data = <DATA>; 
chomp @data; 
 
@data = map  { $_->[0] } 
        sort { $a->[1] cmp $b->[1] or $a->[2] <=> $b->[2] } 
        map  { [ $_, split /: / ] } @data; 
 
print map { "$_\n" } @data; 
 
__END__ 
yaniv : 12 
asaf : 44 
lui : 09 
yaniv : 33

--
Dave Cross, Perl Hacker, Trainer and Writer
http://www.dave.org.uk/
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