note
mreece
array elements are not unique, but hash keys are, so a common approach is to use the uniqueness of hash keys to resolve your array.
<p>
if you want to preserve the original order, you can do this:
<c>
my @nums = qw(2 1 3 5 4 5 4 3 2 1); # order is not important
my @unique; # new list of unique elements
my %seen; # numbers i have seen so far
foreach my $x ( @nums ) { # check each number
if ( ! $seen{$x} ) { # skip if we already saw this one
$seen{$x} = 1; # note we have seen this one now
push @unique, $x; # and store to new list
}
}
## TODO: do something with @unique
</c>
if you want to sort the resulting list, you can do this:
<c>
my @nums = qw(2 1 3 5 4 5 4 3 2 1); # order is not important
my %seen = map { $_ => 1 } @nums; # build a hash; keys will be unique!
@nums = sort keys %seen; # replace old list with new sorted list
## TODO: do something with @nums
</c>
another approach, as rsriram demonstrated above, is to sort first, then loop and look for repeating values:
<c>
my @nums = qw(2 1 3 5 4 5 4 3 2 1);
@nums = sort @nums;
my @unique;
my $previous;
foreach my $current ( @nums ) { # check each number
next if $current eq $previous; # duplicate!
push @unique, $current; # store to new list
$previous = $current; # 'current' becomes 'previous'
}
## TODO: do something with @unique
</c>
(<b>updated</b> to fix some silly issues with untested code)
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