Day 9: array splicing. Quite ugly.

diff --git a/2024/17.pl b/2024/17.pl
new file mode 100755 (executable)
index 0000000..057c733
--- /dev/null
+++ b/2024/17.pl
@@ -0,0 +1,42 @@
+#!/usr/bin/perl -w
+
+use v5.40;
+
+chomp (my $line = <>);
+my $i = 0;
+my @blk = map { [ $i++, $_ ] } split //, $line;
+
+my $bno = 0;
+my $csum;
+sub add_blk($id, $count) {
+       die "$id" if $id % 2;
+       $id = $id/2;
+       $csum += ($bno++ * $id) for (1 .. $count);
+}
+
+my $freesp = 0;
+while (@blk) {
+       if (!$freesp) {
+               my $b = shift @blk;
+               add_blk(@$b);
+               last if !@blk;
+               $freesp = (shift @blk)->[1];
+       }
+
+       my ($eid, $ecnt) = $blk[-1]->@*;
+       if ($freesp < $ecnt) {
+               $blk[-1]->[1] -= $freesp;
+               add_blk($blk[-1]->[0], $freesp);
+               $freesp = 0;
+       } else {
+               last if !@blk;
+               my $b = pop @blk;
+               add_blk(@$b);
+               $freesp -= $b->[1];
+               last if !@blk;
+               pop @blk;
+       }
+}
+
+say $csum;
+

diff --git a/2024/18.pl b/2024/18.pl
new file mode 100755 (executable)
index 0000000..fc01063
--- /dev/null
+++ b/2024/18.pl
@@ -0,0 +1,51 @@
+#!/usr/bin/perl -w
+
+use v5.40;
+
+chomp (my $line = <>);
+my $i = 0;
+my @blk = map { [ $i++, $_ ] } split //, $line;
+
+my $mfile = $#blk;
+my %seen;
+while ($mfile) {
+       my ($id, $count) = $blk[$mfile]->@*;
+       if ($seen{$id}++) {
+               $mfile -= 2;
+               next;
+       }
+
+       my $freesp = 1;
+       while ($freesp < $mfile) {
+               if ($blk[$freesp]->[1] >= $count) {
+                       if ($mfile < $#blk) {
+                               my $free = $blk[$mfile+1]->[1];
+                               splice @blk, $mfile+1, 1;
+                               if ($mfile) {
+                                       $blk[$mfile-1]->[1] += $free + $count;
+                               }
+                       }
+                       splice @blk, $mfile, 1;
+                       my $free = $blk[$freesp]->[1];
+                       splice @blk, $freesp, 1, [ -1, 0 ], [ $id, $count ],
+                               [ -1, $free - $count ];
+                       last;
+               }
+               $freesp += 2;
+       }
+}
+
+my $csum = 0;
+$i = 0;
+my $bno = 0;
+while ($i < @blk) {
+       my ($id, $count) = $blk[$i++]->@*;
+       $id /= 2;
+       $csum += ($bno++ * $id) for (1 .. $count);
+       
+       last if $i >= @blk;
+       ($id, $count) = $blk[$i++]->@*;
+       $bno += $count;
+}
+say $csum;
+