rubyでシーザー暗号解読

caesar.rb

#http://vipprog.net/wiki/exercise.html#h54a0395

class Caesar
  def initialize(str, hint)
    @key = nil
    @str = str
    @base = "abcdefghijklmnopqrstuvwxyz .,-"
    @hint = hint
  end

  def analyze
    1.upto(@base.size-1) do |key|
      @key = key
      hint = shift_hint(@hint)
      next unless @str.index(hint)
      @key = -1 * @key
      break
    end
  end

  def shift_hint(str)
    base_arr = @base.split("")
    str_arr = str.split("")
    shifted = ""
    base_size = base_arr.size
    
    str_arr.each_with_index do |char, i|
      next unless charnum = get_charnum(char)
      next_char = base_arr[(charnum + @key) % base_size]
      shifted << next_char
    end
    shifted
  end

  def get_charnum(char)
    @base.split("").index(char)
  end

end

c = Caesar.new("qdq-gi.q-a ziatmxxitmdqibtqi-ustbi ri.qmoqrcxi.qbubu zir -ibtqi-qp-qaai ripmymsqkir -ibtqi-qy dmxi ri.cnxuoi rruoumxakir -ibtqiqzmobyqzbkii-q.qmxi -imyqzpyqzbi rixmeaki -puzmzoqai -i-qscxmbu zaimzpir -i btq-iymbbq-a;iz -iatmxximzgi.q-a zinqiuzimzgiemgipuao-uyuzmbqpimsmuzabir -ia. za -uzsiacotiimi.qbubu zj", "person")
c.analyze