divide & conquer

def quicksort(arr):
  if not arr or len(arr)<=1: return arr
  pivot = arr[0]
  left = []
  right = []
  for q in arr[1:]:
    if q<=pivot:
      left.append(q)
    else:
      right.append(q)
  return quicksort(left)+[pivot]+quicksort(right)