added improved version

game.rb

@@ -0,0 +1,139 @@
+class Game
+  attr_reader :live_cells, :tick_count
+
+  def initialize(live_cells)
+    @tick_count = 0
+    @live_cells = live_cells # Arr[ [x,y] ]
+  end
+
+  def tick(args=nil)
+    calculate_next_gen
+    render(args)
+    @tick_count += 1
+  end
+
+  private
+
+  attr_writer :live_cells, :tick_count
+
+  def calculate_next_gen
+    next_gen_living_cells = []
+    live_cell_map = convert_cells_to_map
+
+    cells_to_check = calculate_cells_to_check
+
+    cells_to_check.each do |x,y|
+      is_next_gen_living = check_cell(x,y,live_cell_map)
+      next_gen_living_cells << [x,y] if is_next_gen_living
+    end
+    @live_cells = next_gen_living_cells
+  end
+
+  def check_cell(x,y,live_cell_map)
+    adjacent_living_cell_count = adjacent_living_cell_count(x,y,live_cell_map)
+
+    return true if adjacent_living_cell_count == 3
+    return true if adjacent_living_cell_count == 2 && is_living_cell?(x,y,live_cell_map)
+
+    return false
+  end
+
+  def is_living_cell?(x,y,live_cell_map)
+    live_cell_map.dig(x)&.dig(y) == true
+  end
+
+  def convert_cells_to_map
+    map = {}
+    live_cells.each do |x,y|
+      map[x] ||= {}
+      map[x][y] = true
+    end
+
+    map
+  end
+
+  def calculate_cells_to_check
+    cells_to_check = live_cells.dup
+
+    live_cells.each do |x,y|
+      cells_to_check += adjacent_cell_coordinates(x,y)
+    end
+
+    cells_to_check.uniq
+  end
+
+  def adjacent_cell_coordinates(x,y)
+    adjacent_cells = []
+
+    -1.upto(1).each do |i|
+      -1.upto(1).each do |j|
+        adjacent_cells << [x+i,y+j]
+      end
+    end
+    adjacent_cells -= [[x,y]]
+
+    adjacent_cells
+  end
+
+  def adjacent_living_cell_count(x,y,live_cell_map)
+    map = live_cell_map
+    count = 0
+    -1.upto(1).each do |i|
+      -1.upto(1).each do |j|
+        next if i==0 && j==0
+
+        count += 1 if map.dig(x+i)&.dig(y+j)
+      end
+    end
+
+    count
+  end
+
+  def render(args)
+    # print_console
+  end
+
+  def print_console
+    puts "--- Round #{tick_count} ---"
+
+    max_x = live_cells.map{|x,y| x}.max + 5
+    max_y = live_cells.map{|x,y| y}.max + 5
+
+    max_y.times do |y|
+      max_x.times do |x|
+        if live_cells.include? [x,y]
+          print "*"
+        else
+          print "."
+        end
+      end
+      print "\n"
+    end
+  end
+end
+
+# console test
+
+# INPUT = [
+#   [9,9],
+#   [10,10],
+#   [9,11],
+#   [11,11],
+#   [9,12],
+#   [11,12],
+#   [13,13],
+#   [14,13],
+#   [15,13],
+#   [16,13],
+#   [16,15],
+#   [16,16],
+#   [17,17],
+# ]
+
+# game = Game.new(INPUT)
+
+# 100.times do |i|
+#   game.tick
+
+#   sleep 0.2
+# end