adventofcode/14/hash.pm

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Perl
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2017-12-14 18:58:00 +00:00
use 5.20.0;
use List::AllUtils qw/ reduce part /;
use experimental qw/ signatures /;
use base 'Exporter';
our @EXPORT = qw/ knot_hash /;
sub knot_hash ( $string ) {
my @commands = map { ord } split '', $string;
push @commands, 17, 31, 73, 47, 23;
my $skip = 0;
my $i = 0;
my @array = 0..255;
for ( 1..64 ) {
for my $c ( @commands ) {
@array[0..$c-1] = @array[ reverse 0..$c-1];
push @array, shift @array for 1..$c + $skip++;
$i += $c + $skip-1;
}
}
unshift @array, pop @array for 1..($i%@array);
my $j;
my @grouped = map {
reduce { $a ^ $b } @$_
} part { $j++ / 16 } @array;
return join '', map { sprintf "%02x", $_ } @grouped;
}