shuffles array method.

shuffle.rb

# Array#shuffle returns to shuffled self.
# Array#shuffle! destructive shuffles to self.
# [1, 2, 3, 4, 5].shuffle # => [2, 1, 5, 4, 3] (example)

class Array

  def shuffle
    clone.shuffle!
  end

  def shuffle!
    tmp = clone
    clear
    push(tmp.delete(tmp.sample)) until tmp.empty?
    self
  end

end