day14

14/1.pl

@@ -0,0 +1,14 @@
+use 5.20.0;
+
+use lib '.';
+use hash;
+my $key = 'stpzcrnm';
+
+use List::AllUtils qw/ sum /;
+
+say sum
+    map { split '' }
+    map { sprintf "%04b", $_ }
+    map { hex }
+    map { split '' }
+    map { knot_hash( join '-', $key, $_) } 0..127;

14/2.pl

@@ -0,0 +1,36 @@
+use 5.20.0;
+
+use lib '.';
+use hash;
+my $key = 'stpzcrnm';
+
+use List::AllUtils qw/ sum /;
+
+my @grid =
+    map { [ map { $_ ? '#' : ' ' } map { split '', sprintf "%04b", hex } split '' ] }
+    map { knot_hash( join '-', $key, $_) } 0..127;
+
+my $clusters;
+for my $x ( 0..127 ) {
+    for my $y ( 0..127 ) {
+        $clusters+= eradicate(\@grid,$x,$y);
+    }
+}
+
+say $clusters;
+
+use experimental qw/ signatures /;
+sub eradicate($grid,$i,$j) {
+        return 0 if $grid->[$i][$j] ne '#';
+        $grid->[$i][$j] = ' ';
+        eradicate($grid,$i-1,$j) if $i > 0;
+        eradicate($grid,$i,$j-1) if $j > 0;
+        eradicate($grid,$i+1,$j);
+        eradicate($grid,$i,$j+1);
+        return 1;
+}
+
+
+sub print_g {
+    say @$_ for @grid;
+}

14/hash.pm

@@ -0,0 +1,34 @@
+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;
+}