Quick-sort Algorithm

quicksort.rb

def quick_sort(arr)
  return arr if arr.length <= 1
  pivot = arr.pop
  less_than_pivot = arr.select { |x| x < pivot }
  greater_than_pivot = arr.select { |x| x > pivot }
  quick_sort(less_than_pivot) + [pivot] + quick_sort(greater_than_pivot)
end

print quick_sort([1,5,9,2,45,2,3,4,4545])