。包括？数组[rand(array.length)]

Question

我正在尝试编写 shuffle 方法的替代方法，但不明白为什么它会返回重复项。有没有人看到问题？非常感谢！

def return_random_songs(songs)
  returned_songs = []
  while returned_songs.length < songs.length
    unless returned_songs.include?(songs[rand(songs.length)])
      returned_songs << songs[rand(songs.length)]
    end
  end
  return returned_songs
end

songs = ["song 1", "song 2", "song 3", "song 4"]
pp return_random_songs(songs)
=> ["song 2", "song 4", "song 1", "song 1"] #duplicates!

Answer 1

因为您计算了两次随机歌曲：用于检查和添加歌曲时（因此您不知道 returned_songs 数组中的最终结果）。试试

def return_random_songs(songs)
  returned_songs = []
  while returned_songs.length < songs.length
    random_song = songs[rand(songs.length)]
    unless returned_songs.include?(random_song)
      returned_songs << random_song
    end
  end
  return returned_songs
end