Day 18: quite fast program, but slow to write

[aoc.git] / 2023 / 36.pl

diff --git a/2023/36.pl b/2023/36.pl
new file mode 100755 (executable)
index 0000000..956c980
--- /dev/null
+++ b/2023/36.pl
@@ -0,0 +1,95 @@
+#!/usr/bin/perl -w
+
+use v5.38;
+
+my ($x, $y) = (20_000_000, 20_000_000);
+my %dir = (
+       0 => [ 1,  0 ],
+       1 => [ 0,  1 ],
+       2 => [ -1, 0 ],
+       3 => [ 0, -1 ],
+);
+
+my %map;
+my %dirs;
+while (<>) {
+       my ($len, $dir) = /\(\#(\w+)(\w)\)/;
+       $len = hex $len;
+       $map{$y}{$x} |= (1 << $dir);
+       $x += $len * $dir{$dir}->[0];
+       $y += $len * $dir{$dir}->[1];
+       $map{$y}{$x} |= (1 << ($dir ^ 2));
+       say "at $x,$y dir $dir len $len";
+}
+
+sub sum_int {
+       my @pts = @_;
+       my $sum = 0;
+       my $in;
+       my $prev;
+       for my $pt (@pts) {
+               if (defined $prev && $in) {
+                       $sum += $pt - $prev + 1;
+               }
+               $prev = $pt;
+               $in = !$in;
+       }
+       return $sum;
+}
+
+my @pts;
+my $y0;
+my $sum;
+for my $y1 (sort { $a <=> $b } keys %map) {
+       say "y $y1";
+       my $in;
+       my $x0;
+       my @nx;
+       my @tx;
+       my $rowsum;
+       if (defined $y0) {
+               my $psum = sum_int(@pts);
+               $sum += ($y1-$y0-1) * $psum;
+       }
+
+       for my $x1 (sort { $a <=> $b } (@pts, keys %{ $map{$y1} })) {
+               next if $x0 && $x1 == $x0;
+               my $d = $map{$y1}{$x1};
+               my $d0 = $map{$y1}{$x0} if defined $x0;
+               say " at $x1,$y1 ", $d // "|";
+               push @nx, $x1
+                       if !defined $d || ($d & 2);
+               if (!defined $d) {
+                       push @tx, $x1;
+               } elsif ($d & 4) {
+                       if (@tx & 1) {
+                               if (($d0 == 9 && $d == 6) || ($d0 == 3 && $d == 12)) {
+                                       push @tx, $x1;
+                               }
+                       } else {
+                               push @tx, $x0;
+                               if (($d0 == 9 && $d == 12) || ($d0 == 3 && $d == 6)) {
+                                       push @tx, $x1;
+                               }
+                       }
+               }
+
+               if (defined $x0) {
+                       say "   int $x0 .. $x1";
+                       
+                       $in = !$in;
+                       if ($in) {
+                               $rowsum += $x1 - $x0 + 1;
+                       }
+               }
+               $x0 = $x1;
+       }
+       $sum += sum_int(@tx);
+       say " tx=@tx sum ", sum_int(@tx);
+       say " nx=@nx sum ", sum_int(@nx);
+       @pts = @nx;
+       $y0 = $y1;
+}
+
+say $sum;
+