How can I delete duplicate values across arrays stored in hash? - arrays

Question

I have the following hash:
my %HASH = (
'List1' => [ 'the', 'red', 'cat', 'jumps' ],
'List2' => [ 'the', 'brown', 'fox', 'jumps' ],
'List3' => [ 'a', 'red', 'fox', 'jumps' ],
);
I want to delete duplicate elements across these arrays, so that only unique elements remain. The desired output would be the following:
my %HASH = (
'List1' => [ 'cat' ],
'List2' => [ 'brown' ],
'List3' => [ 'a' ],
);
In other words, if an element is present in both List1 and List2, it should be deleted from both lists.
I have tried to do the following:
use strict;
use warnings;
use diagnostics;
use Data::Dumper;
foreach my $key ( keys %HASH ) {
foreach ( #{$HASH{$key}} ) {
if(exists($HASH{$key})){
#{$HASH{$key}} = delete($HASH{$key});
}
}
}
print Dumper(\%HASH);
Which doesn't seem to do anything, the hash remains the way it was. I'm still pretty new to Perl, so I'm not sure where I went wrong with that. But Perldoc says that calling exists on array values is deprecated anyway, so any solution which uses something other than exists is welcome too!

Answer 1

use strict;
use warnings;
my %hash = (
'List1' => [ 'the', 'red', 'cat', 'jumps' ],
'List2' => [ 'the', 'brown', 'fox', 'jumps' ],
'List3' => [ 'a', 'red', 'fox', 'jumps' ],
);
# first, we count all words
my %count;
for my $words (values %hash) {
for my $word (#$words) {
$count{$word}++;
}
}
# Now, we filter the words with `grep` so that only
# those remain which were found once
for my $words (values %hash) {
#$words = grep { $count{$_} == 1 } #$words;
}
use Data::Dump;
dd \%hash;
Outputs:
{ List1 => ["cat"], List2 => ["brown"], List3 => ["a"] }