Basic quick sort implementation, unoptimized

qsort.rb

def qsort(list)
  return list unless list.length > 1
  pivot_index = rand(0...list.length)
  pivot = list[pivot_index]
  less = []
  greater = []
  list.delete_at(pivot_index)
  list.each do |el|
    (if el > pivot then greater else less end) << el
  end
  (qsort(less) << pivot << qsort(greater)).flatten
end