「🎉」 init(2025): day 1

2024/day08/part1.rb

@@ -0,0 +1,47 @@
+require 'set'
+
+if File.exists?("input.txt")
+  file = File.open("input.txt")
+  file_data = file.read
+  file.close
+else
+  file_data = "............\n........0...\n.....0......\n.......0....\n....0.......\n......A.....\n............\n............\n........A...\n.........A..\n............\n............"
+end
+
+antennas = []
+map = file_data.split("\n")
+map.each_with_index do |row, r|
+  row.chars.each_with_index do |char, c|
+    antennas << [c, r, char] if char != '.'
+  end
+end
+
+antinodes = Set.new
+
+antennas.each_with_index do |(x1, y1, value1), i|
+  antennas.each_with_index do |(x2, y2, value2), j|
+    next if i == j
+    next unless  value1 == value2
+
+    x_dir = x2 - x1
+    y_dir = y2 - y1
+
+    [1, -1].each do |dir|
+      if dir > 0
+        x_point = x1 - x_dir * dir
+      else
+        x_point = x2 - x_dir * dir
+      end
+      
+      if dir > 0
+        y_point = y1 - y_dir * dir
+      else
+        y_point = y2 - y_dir * dir
+      end
+
+      antinodes.add([x_point, y_point]) if (x_point.between?(0, map.size - 1) && y_point.between?(0, map[0].size - 1))
+    end
+  end
+end
+
+puts antinodes.size