input: Write a python function to find the maximum element in a list using divide and conquer strategy.
  assert max_list_div_conq([1, 5, 3, 9, 2]) == 9
  assert max_list_div_conq([10, 20, 5, 6, 30, 12]) == 30
  assert max_list_div_conq([7, 4, 8, 1, 2, 0, 9]) == 9
output: def max_list_div_conq(arr):
      if len(arr) == 1:
          return arr[0]
      mid = len(arr) // 2
      left_max = max_list_div_conq(arr[:mid])
      right_max = max_list_div_conq(arr[mid:])
      return max(left_max, right_max)