input: Write a python function to sort a list of integers using the quicksort algorithm.
  assert quickSort([9, 5, 7, 4, 3, 10], 0, 5) == [3, 4, 5, 7, 9, 10]
  assert quickSort([1, 2, 3, 4, 5], 0, 4) == [1, 2, 3, 4, 5]
  assert quickSort([5, 4, 3, 2, 1], 0, 4) == [1, 2, 3, 4, 5]
output: def quickSort(arr, low, high):
      if low < high:
          pi = partition(arr, low, high)
          quickSort(arr, low, pi - 1)
          quickSort(arr, pi + 1, high)
      return arr
  
  def partition(arr, low, high):
      pivot = arr[high]
      i = low - 1
      for j in range(low, high):
          if arr[j] < pivot:
              i += 1
              arr[i], arr[j] = arr[j], arr[i]
      arr[i + 1], arr[high] = arr[high], arr[i + 1]
      return i + 1