From: Jan "Yenya" Kasprzak <kas@fi.muni.cz>
Date: Thu, 4 Dec 2025 07:28:57 +0000 (+0100)
Subject: Day 4 part 2: shorter solution
X-Git-Url: https://www.fi.muni.cz/~kas/git//home/kas/public_html/git/?a=commitdiff_plain;h=238b94912013e91b8d8c34110fd06b474af880bc;p=aoc.git

Day 4 part 2: shorter solution
---

diff --git a/2025/08.pl b/2025/08.pl
index 3e4d8bf..fe63bd6 100755
--- a/2025/08.pl
+++ b/2025/08.pl
@@ -3,7 +3,7 @@
 use v5.42;
 
 my @map = map { chomp; [ split // ] } <>;
-my $xmax = $#{ $map[0] };
+my $xmax = $map[0]->$#*;
 my $ymax = $#map;
 
 my $sum;
@@ -14,24 +14,22 @@ while (1) {
 		for my $x (0 .. $xmax) {
 			next if $map[$y][$x] ne '@';
 			my $c = 0;
-			for my $dy (-1 .. 1) {
-				my $ny = $y + $dy;
-				next if $ny < 0 || $ny > $ymax;
-				for my $dx (-1 .. 1) {
-					next if $dy == 0 && $dx == 0;
-					my $nx = $x + $dx;
-					next if $nx < 0 || $nx > $xmax;
-					$c++ if $map[$ny][$nx] eq '@';
-				}
+			for my $dir ([-1, -1], [-1, 0], [-1, 1],
+			             [ 0, -1],          [ 0, 1],
+			             [ 1, -1], [ 1, 0], [ 1, 1]) {
+				my ($nx, $ny) = ($x + $dir->[0], $y + $dir->[1]);
+				next if $nx < 0 || $nx > $xmax
+				     || $ny < 0 || $ny > $ymax;
+				$c++ if $map[$ny][$nx] eq '@';
 			}
 			push @to_remove, [$x, $y] if $c < 4;
 		}
 	}
-	last if !@to_remove;
 	for my $p (@to_remove) {
 		$map[$p->[1]][$p->[0]] = '.';
 		$sum++;
 	}
+	last if !@to_remove;
 }
 
 say $sum;