From 773b37cfb0211a65d3a05bc60b7b70e79db5b881 Mon Sep 17 00:00:00 2001
From: Christian Segundo
Date: Wed, 4 Dec 2024 10:27:58 +0100
Subject: add day 4

---
 4.pl | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 4.pl

(limited to '4.pl')

diff --git a/4.pl b/4.pl
new file mode 100644
index 0000000..110708a
--- /dev/null
+++ b/4.pl
@@ -0,0 +1,39 @@
+#!/usr/bin/env perl
+open(my $fh, "4-input.txt") or die ;
+while (<$fh>) { chomp; push @lines, [split //]; }
+close($fh);
+
+my $xmas_count = 0;
+my $mas_count = 0;
+
+for ($i = 0; $i < scalar @lines; $i++) {
+    my @line = @{ $lines[$i] };
+    for($j=0; $j < scalar @line; $j++) {
+      if ($i+3 < scalar @lines) {
+        if ($j+3 < scalar @line and $line[$j] eq 'X' and $lines[$i+1][$j+1] eq 'M' and $lines[$i+2][$j+2] eq 'A' and $lines[$i+3][$j+3] eq 'S') { $xmas_count++; }
+        if ($j-3 >= 0 and $line[$j] eq 'X' and $lines[$i+1][$j-1] eq 'M' and $lines[$i+2][$j-2] eq 'A' and $lines[$i+3][$j-3] eq 'S') { $xmas_count++; }
+        if ($line[$j] eq 'X' and $lines[$i+1][$j] eq 'M' and $lines[$i+2][$j] eq 'A' and $lines[$i+3][$j] eq 'S') { $xmas_count++; }
+      }
+
+      if ($i-3 >= 0) {
+        if ($j+3 < scalar @line and $line[$j] eq 'X' and $lines[$i-1][$j+1] eq 'M' and $lines[$i-2][$j+2] eq 'A' and $lines[$i-3][$j+3] eq 'S') { $xmas_count++; }
+        if ($j-3 >= 0 and $line[$j] eq 'X' and $lines[$i-1][$j-1] eq 'M' and $lines[$i-2][$j-2] eq 'A' and $lines[$i-3][$j-3] eq 'S') { $xmas_count++; }
+        if ($line[$j] eq 'X' and $lines[$i-1][$j] eq 'M' and $lines[$i-2][$j] eq 'A' and $lines[$i-3][$j] eq 'S') { $xmas_count++; }
+      }
+
+      if ($j+3 < scalar @line and $line[$j] eq 'X' and $line[$j+1] eq 'M' and $line[$j+2] eq 'A' and $line[$j+3] eq 'S') { $xmas_count++; }
+      if ($j-3 >= 0 and $line[$j] eq 'X' and $line[$j-1] eq 'M' and $line[$j-2] eq 'A' and $line[$j-3] eq 'S') { $xmas_count++; }
+
+      if ($line[$j] eq 'A' and $i-1>=0 and $j-1>=0 and $i+1<scalar @lines and $j+1 <scalar @line) {
+        $k = 0;
+        if ($lines[$i-1][$j-1] eq 'M' and $lines[$i+1][$j+1] eq 'S') { $k++; }
+        if ($lines[$i-1][$j+1] eq 'M' and $lines[$i+1][$j-1] eq 'S') { $k++; }
+        if ($lines[$i+1][$j-1] eq 'M' and $lines[$i-1][$j+1] eq 'S') { $k++; }
+        if ($lines[$i+1][$j+1] eq 'M' and $lines[$i-1][$j-1] eq 'S') { $k++; }
+        if ($k > 1) { $mas_count++; }
+      }
+    }
+}
+
+print "puzzle 1: $xmas_count\n";
+print "puzzle 2: $mas_count\n";
-- 
cgit v1.2.3