[2023][ruby][16.2] shameless green

2023/ruby/day_16.rb

@@ -3,10 +3,11 @@ input = ARGF.readlines(chomp: true)
     row.chars.map.with_index {|elem, x| [[y,x], elem] }
   }.to_h
 
-current = [[[0,0], [0,1]]]
-seen = Set.new
+count_energized = ->(start, dir) {
+  current = [[start, dir]]
+  seen = Set.new
 
-until current.empty?
+  until current.empty?
     coord, delta = current.shift
     seen << [coord, delta]
 
@@ -42,6 +43,19 @@ until current.empty?
     end
 
     current = current.reject { seen.include?(_1) }
-end
+  end
+
+  seen.map(&:first).select { input.has_key?(_1) }.uniq.size
+}
+
+max_y = input.keys.map(&:first).max
+max_x = input.keys.map(&:last).max
+
+candidates = [
+  (0..max_x).map { [[0,_1], [1,0]] },      # down
+  (0..max_x).map { [[max_y,_1], [-1,0]] }, # up
+  (0..max_y).map { [[_1,0], [0,1]] },      # right
+  (0..max_y).map { [[_1,max_x], [0,-1]] }, # left
+].inject(:+)
 
-p seen.map(&:first).select { input.has_key?(_1) }.uniq.size
+p candidates.map { count_energized[*_1] }.max