day15

15/1.pl

@@ -0,0 +1,18 @@
+use 5.20.0;
+
+use List::AllUtils qw/ pairgrep /;
+
+my @v = ( 679,771 );
+
+my $mask = 2**16 - 1;
+
+my $match;
+for ( 1..40_000_000 ) {
+    @v = ( 16807 * $v[0], 48271 * $v[1] );
+    $_ %= 2147483647 for @v;
+
+    $match += ($v[0] & $mask) == ($v[1] & $mask);
+
+}
+
+say $match;

15/2.pl

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+use 5.20.0;
+
+use List::Lazy qw/ lazy_list lazy_range /;
+
+my $mask = 2**16 - 1;
+
+my $list_a = ( lazy_list {
+    $_ *= 16_807;
+    $_ %= 2147483647;
+    $_;
+} 679 )->grep( sub { not $_ % 4 } )->map(sub{ $_ & $mask });
+
+my $list_b = ( lazy_list {
+    $_ *= 48_271;
+    $_ %= 2147483647;
+    $_;
+} 771 )->grep( sub { not $_ % 8 } )->map(sub{ $_ & $mask });
+
+
+use DDP;
+my $i = 0;
+say $list_a
+    ->until(sub{ ++$i >= 5_000_000})
+    ->spy(sub { say $i unless $i % 100_000 })
+    ->grep(sub { $_ == $list_b->next } )
+    ->reduce(sub { $a + 1},0);
+

15/input.txt

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+Generator A starts with 679
+Generator B starts with 771