Add 2023 day 10, part two

2023/day10/day10b

@@ -17,32 +17,25 @@ class RouteFinder
 
   def move
     pos = @route.last
-    warn "looking at #{pos}"
     [
       {coords: {x: pos[:x] - 1, y: pos[:y]}, good_from: "S-7J", good_to: "S-LF"},
       {coords: {x: pos[:x] + 1, y: pos[:y]}, good_from: "S-FL", good_to: "S-J7"},
       {coords: {x: pos[:x], y: pos[:y] - 1}, good_from: "S|JL", good_to: "S|7F"},
       {coords: {x: pos[:x], y: pos[:y] + 1}, good_from: "S|7F", good_to: "S|JL"}
     ].each do |next_pos|
-      warn "considering #{next_pos}"
       next unless on_sketch?(next_pos[:coords])
-      warn "#{next_pos} is on sketch"
 
       tile = @sketch[next_pos[:coords][:y]][next_pos[:coords][:x]]
-      warn "tile: #{tile}"
 
       next unless next_pos[:good_from].include?(pos[:tile])
       next unless next_pos[:good_to].include?(tile)
 
       if tile == "S" && @route.length > 2
-        warn "looped around to start!"
         @finished = true
         break
       end
 
-      warn "#{tile} could connect"
       next if route.length > 1 && same_pos?(next_pos[:coords], route[-2])
-      warn "#{next_pos} is not moving backwards, is next!"
 
       route << next_pos[:coords].merge({tile: tile})
       break
@@ -51,12 +44,53 @@ class RouteFinder
 
   def finished? = @finished
 
+  def filtered
+    @filtered ||= @sketch.map.with_index do |row, y|
+      row.map.with_index do |tile, x|
+        route_set.include?({x: x, y: y, tile: tile}) ? tile : "."
+      end.map { |tile| tile.tr("-|F7LJ", "─│┌┐└┘") }
+    end
+
+    # Replace "S" with correct pipe
+    prev_x = @route[-1][:x]
+    prev_y = @route[-1][:y]
+    next_x = @route[1][:x]
+    next_y = @route[1][:y]
+    @filtered[@route[0][:y]][@route[0][:x]] = case
+    when (next_x - prev_x).abs == 2 then "─"
+    when (next_y - prev_y).abs == 2 then "│"
+    when next_x == prev_x - 1 && next_y == prev_y - 1 then "┐"
+    when next_x == prev_x + 1 && next_y == prev_y - 1 then "┌"
+    when next_y == prev_y + 1 && next_x == prev_x + 1 then "┘"
+    when next_y == prev_y + 1 && next_x == prev_x - 1 then "└"
+    end
+
+    @filtered
+  end
+
   def draw_route
-    filtered = @sketch.map.with_index do |row, y|
-      row.map.with_index { |tile, x| route.include?({x: x, y: y, tile: tile}) ? tile : "." }.join
+    puts filtered.map(&:join)
+  end
+
+  def count_enclosed
+    enclosed = 0
+    re = /│|┌─*┘|└─*┐/
+    filtered.each_with_index do |line, y|
+      line.each_with_index do |tile, x|
+        next if tile != "."
+        next if line[...x].all? { |tile| tile == "." }
+        next if line[x..].all? { |tile| tile == "." }
+        next unless line[x + 1..].join.scan(re).length.odd?
+
+        enclosed += 1
+      end
     end
 
-    puts filtered
+    enclosed
+  end
+
+  private def route_set
+    @route_set ||= Set.new(@route)
   end
 
   private def on_sketch?(point)
@@ -73,4 +107,4 @@ file = File.open(ARGV[0])
 finder = RouteFinder.new(file.readlines)
 finder.move until finder.finished?
 
-puts finder.route.length / 2
+puts finder.count_enclosed