Re: unique elements in an array

If you want to keep the items in order by first appearance, try using a side hash as an insertion guard.

use strict;
 
my %guard;
my @unique;
 
while (<>) {
   chomp;
   push @unique,$_ if (!exists $guard{$_});
   $guard{$_} = 1;
}
print join(" ",@unique),"\n";
[download]

Comment on Re: unique elements in an array Download Code

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Re^2: unique elements in an array by dragonchild (Archbishop) on Feb 23, 2005 at 18:01 UTC
Good code. A few optimizations: `use strict; my %guard; my @unique; while (<>) { chomp; next if exists $guard{$_}; push @unique,$_; $guard{$_} = undef; } print join(" ",@unique),"\n";` [download] A slight improvement in speed and memory usage, especially when you are dealing with a large number of duplicates. Being right, does not endow the right to be rude; politeness costs nothing. Being unknowing, is not the same as being stupid. Expressing a contrary opinion, whether to the individual or the group, is more often a sign of deeper thought than of cantankerous belligerence. Do not mistake your goals as the only goals; your opinion as the only opinion; your confidence as correctness. Saying you know better is not the same as explaining you know better.	[reply] [d/l]

Replies are listed 'Best First'.

Re^2: unique elements in an array
by dragonchild (Archbishop) on Feb 23, 2005 at 18:01 UTC

use strict;
 
my %guard;
my @unique;
 
while (<>) {
   chomp;
   next if exists $guard{$_};

   push @unique,$_;
   $guard{$_} = undef;
}
print join(" ",@unique),"\n";
[download]

A slight improvement in speed and memory usage, especially when you are dealing with a large number of duplicates.

Being right, does not endow the right to be rude; politeness costs nothing.
Being unknowing, is not the same as being stupid.
Expressing a contrary opinion, whether to the individual or the group, is more often a sign of deeper thought than of cantankerous belligerence.
Do not mistake your goals as the only goals; your opinion as the only opinion; your confidence as correctness. Saying you know better is not the same as explaining you know better.

[reply]
[d/l]