input: Write a function to calculate the difference between the lowest and highest value for an array of integers.
  def diffHighestLowest(arr):
      if not arr:
          return 0
      return max(arr) - min(arr)
  
  assert diffHighestLowest([12, 24, 3, 8, -1]) == 25
  assert diffHighestLowest([-5, -10, -2, -7, -3]) == 8
  assert diffHighestLowest([0, 0, 0, 0]) == 0
  assert diffHighestLowest([]) == 0
  assert diffHighestLowest([5]) == 0
output: def diffHighestLowest(arr):
      if not arr:
          return 0
      return max(arr) - min(arr)