def quick_sort(nums):

if len(nums) == 0: return nums

if len(nums) == 1: return nums

pivot = nums[0]

left = 1

for right in range(1, len(nums)):

if nums[right] < pivot:

nums[left], nums[right] = nums[right], nums[left]

left += 1

left -= 1

nums[0], nums[left] = nums[left], nums[0]

left_ans = quick_sort(nums[:left])

right_ans = quick_sort(nums[left + 1:])

return left_ans + [nums[left]] + right_ans

if __name__ == "__main__":

nums = [54, 26, 93, 17, 77, 31, 44, 55, 20]

print(quick_sort(nums))