diff --git a/2018/ruby/day_04.rb b/2018/ruby/day_04.rb
index 36c3732..61d945c 100644
--- a/2018/ruby/day_04.rb
+++ b/2018/ruby/day_04.rb
@@ -11,19 +11,19 @@ records.each do |record|
   elsif record =~ /\[\d{4}-\d{2}-\d{2} \d{2}:(\d{2})\] falls asleep/
     fell_asleep_at = $1.to_i
   elsif record =~ /\[\d{4}-\d{2}-\d{2} \d{2}:(\d{2})\] wakes up/
-    stats[guard] << (fell_asleep_at...$1.to_i)
+    stats[guard].concat((fell_asleep_at...$1.to_i).to_a)
   else
     p record
   end
 end
 
+stats.transform_values! {|v| v.group_by {|x| x }.transform_values(&:count) }
+
 # Part One
-guard, ranges = stats.max_by {|_,v| v.map(&:size).sum }
-minute = ranges.flat_map(&:to_a).group_by {|x| x }.transform_values(&:count).max_by(&:last).first
+guard, minutes = stats.max_by {|_,v| v.values.sum }
+minute = minutes.max_by(&:last).first
 p guard * minute
 
 # Part Two
-guard, (minute, _) = stats.map {|k,v|
-  [k, v.flat_map(&:to_a).group_by {|x| x }.transform_values(&:count).max_by(&:last)]
-}.max_by {|_,(_,v)| v }
+guard, (minute, _) = stats.map {|k,v| [k, v.max_by(&:last)] }.max_by {|_,(_,v)| v }
 p guard * minute