input: Write a function to calculate the difference between the lowest and highest value for an array of integers. If the array is empty, return 0.
  
  
  def diffHighestLowest(arr):
      if not arr:
          return 0
      lowest = min(arr)
      highest = max(arr)
      return highest - lowest
  
  assert diffHighestLowest([12, 24, 3, 8, -1]) == 25
  assert diffHighestLowest([7, 3, 9, 5]) == 6
  assert diffHighestLowest([-2, -5, -8, -1]) == 7
  assert diffHighestLowest([]) == 0
  
output: def diffHighestLowest(arr):
      if not arr:
          return 0
      lowest = min(arr)
      highest = max(arr)
      return highest - lowest