[2016][ruby][21.1]

2016/ruby/day_21.rb

@@ -1,5 +1,7 @@
-input = 'abcdefgh'
-ARGF.read.split("\n").each do |instruction|
+INSTRUCTIONS = ARGF.read.split("\n")
+
+def scramble(input)
+  INSTRUCTIONS.each do |instruction|
     case instruction
     when /swap position (\d+) with position (\d+)/
       x = $1.to_i
@@ -34,4 +36,13 @@ ARGF.read.split("\n").each do |instruction|
       raise "invalid instruction: '#{instruction}'"
     end
   end
-puts input
+  input
+end
+
+input = 'abcdefgh'.chars
+input.permutation.each do |candidate|
+  if scramble(candidate.join) == 'fbgdceah'
+    puts candidate.join
+    exit
+  end
+end