Day 23: quite slow to write

[aoc.git] / 2023 / 45.pl

diff --git a/2023/45.pl b/2023/45.pl
new file mode 100755 (executable)
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--- /dev/null
+++ b/2023/45.pl
@@ -0,0 +1,41 @@
+#!/usr/bin/perl -w
+
+use v5.38;
+use experimental 'multidimensional';
+$; = ',';
+
+my @map = map { chomp; [ split // ] } <>;
+my $xmax = $#{ $map[0] };
+my $ymax = $#map;
+
+my @dx = (1, 0, -1, 0);
+my @dy = (0, 1, 0, -1);
+
+my %seen;
+my @q = [ 1, 1, 1, [1, 1] ];
+while (@q) {
+       my ($x, $y, $steps, @path) = @{ shift @q };
+
+       next if $seen{$x,$y} && $seen{$x,$y} > $steps;
+       $seen{$x,$y} = $steps;
+       if ($x == $xmax-1 && $y == $ymax) {
+               say "at $x,$y, $steps, ", join(' ', map { "[$_->[0],$_->[1]]" } @path);
+               say "path len $steps";
+               next;
+       }
+       my %visited;
+       $visited{$_->[0],$_->[1]} = 1 for @path;
+       for my $d (0 .. 3) {
+               my $nx = $x + $dx[$d];
+               my $ny = $y + $dy[$d];
+               next if $map[$ny][$nx] eq '#';
+               next if $ny == 0;
+               next if $visited{$nx,$ny};
+               next if $d != 0 && $map[$y][$x] eq '>';
+               next if $d != 1 && $map[$y][$x] eq 'v';
+               next if $d != 2 && $map[$y][$x] eq '<';
+               next if $d != 3 && $map[$y][$x] eq '^';
+               push @q, [ $nx, $ny, $steps+1, @path, [ $nx, $ny ] ];
+       }
+}
+