quick sort implementation in ruby

quick_sort.rb

def quick_sort(list)
  return list.dup unless list.size > 1

  x = list.sample

  h = list.group_by { |item| item <=> x }
  h.default = []

  less, equal, more = h[-1], h[0], h[1]

  quick_sort(less) + equal + quick_sort(more)
end