[day16] Had an inspiration about part 2

1 files changed, 41 insertions, 0 deletions

diff --git a/day16/part2 b/day16/part2
new file mode 100755
index 0000000..e494f16
--- /dev/null
+++ b/day16/part2
@@ -0,0 +1,41 @@
+#!/usr/bin/env ruby
+
+input = gets.chomp.split(',')
+
+startline = %w( a b c d e f g h i j k l m n o p )
+line = startline.dup
+i = 0
+
+def dodance(line, dance)
+  dance.each do |istr|
+    case istr[0]
+    when 's'
+      n = istr[1..-1].to_i
+      line = line[-n..-1] + line[0..-n-1]
+    when 'x'
+      ns = istr[1..-1].split('/').map(&:to_i)
+      t = line[ns[0]]
+      line[ns[0]] = line[ns[1]]
+      line[ns[1]] = t
+    when 'p'
+      ps = istr[1..-1].split('/')
+      i0 = line.index(ps[0])
+      i1 = line.index(ps[1])
+      line[i0] = ps[1]
+      line[i1] = ps[0]
+    end
+  end
+  line
+end
+
+loop do
+  line = dodance(line, input)
+  i += 1
+  break if line == startline
+end
+
+(1_000_000_000 % i).times do
+  line = dodance(line, input)
+end
+
+puts line.join