オフラインリアルタイムどう書く18回の参考問題を、rubyで

def solve( x )
  return "" if x.empty? || ! x
  r=solve( x[1..-1] )
  i=r.tr("mV", "Vm").reverse
  case x[0]
  when "L"; i+"V"+r
  when "J"; r+"V"+i
  when "Z"; r+"m"+i+"V"+r
  when "S"; r+"V"+i+"m"+r
  when "U"; i+"V"+r+"V"+i
  else; raise "#{x}"
  end
end

$stdout.sync=true

DATA.map{ |line|
  num, src, expected = line.split( /\s+/ )
  actual = solve( src )
  ok = actual==expected;
  puts "%s %s->%s ( %s )" % [ ok ? "ok" : "***NG***", src, actual, expected ]
  ok
}.tap{ |x| p x.all? }

__END__
0 JZ  mVVmV