input: Write a function to calculate the difference between the lowest and highest value for an array of integers.
  
  
  def diffHighestLowest(arr):
      lowest = min(arr)
      highest = max(arr)
      return highest - lowest
  
  assert diffHighestLowest([12, 24, 3, 8, -1]) == 25
  assert diffHighestLowest([5, 10, 20, 30, 40]) == 35
  assert diffHighestLowest([-10, -20, -30, -40]) == 30
  assert diffHighestLowest([1]) == 0
  assert diffHighestLowest([]) == 0
  
output: def diffHighestLowest(arr):
      if not arr:
          return 0
      lowest = min(arr)
      highest = max(arr)
      return highest - lowest