Solution for Day 11

day_11/first.rb

@@ -0,0 +1,50 @@
+input = File.readlines('./input').map(&:strip).map(&:chars)
+
+$dirs = [
+  [-1,-1],
+  [-1,0],
+  [-1,1],
+  [0,-1],
+  [0,1],
+  [1,-1],
+  [1,0],
+  [1,1]
+]
+
+
+def round(map)
+  output = []
+  map.each_index do |row|
+    output << []
+    map[row].each_index do |col|
+      tmp = $dirs.map do |x, y|
+        x_index = row + x
+        y_index = col + y
+
+        next nil if x_index < 0 || y_index < 0
+        map[row+x]&.[](col+y)
+      end
+      occupied = tmp.compact.count('#')
+      output[row][col] = case [map[row][col], occupied]
+      in ['L', 0]
+        '#'
+      in ['#', 4..]
+        'L'
+      else
+        map[row][col]
+      end
+    end
+  end
+
+  output
+end
+
+last_hash = 0
+out = input
+
+until out.hash == last_hash
+  last_hash = out.hash
+  out = round out
+end
+
+puts out.map{_1.count('#')}.inject(:+)