Day 09

Author: petertseng

09_stream_of_garbage.rb

@@ -0,0 +1,33 @@
+input = ARGF.read.chomp
+
+# Remove the ! and characters they cancel.
+# This only works given that gsub does not find overlapping groups
+# (so that !!x turns into x, not empty string)
+# and that ! and the char it cancels aren't counted in garbage.
+input.gsub!(/!./, '')
+
+score = 0
+open_groups = 0
+garbage = false
+garbages = 0
+
+input.each_char { |x|
+  garbages += 1 if garbage && x != ?>
+
+  case x
+  when ?{
+    open_groups += 1 unless garbage
+  when ?}
+    unless garbage
+      score += open_groups
+      open_groups -= 1
+    end
+  when ?<
+    garbage = true
+  when ?>
+    garbage = false
+  end
+}
+
+puts score
+puts garbages