I have an array that has multiple entries of the same element in it. I want to make a new array with just the unique elements in it. How can this be done?

Pretty much every time you see the word "unique" in a problem, you want a hash. For this, I'd take a two-pass approach: tally the elements of the array, then pick out the unique ones. So:

my %elem_count = ();

for my $elem (@array) {
  $elem_count{$elem}++;
}

my @uniques = ();

for my $elem (keys %elem_count) {
  push @uniques, $elem if $elem_count{$elem} == 1;
}

[download]

So (to be brutally obvious) we're storing the number of times we see each element in the hash %elem_count, then going through %elem_count key by key, picking out the ones that have a count of 1. (Of course, you can do the first bit at the same time as you're inserting elements in the array, which may or may not be practical.)

As for your second question, I confess I don't really see the problem. Unless you've been mucking around with $/, $_ will contain the line you just read in at every pass through the while.

--
:wq

In reply to Re: Deciding unique elements of an array by FoxtrotUniform
in thread Deciding unique elements of an array by Spliter

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