input: Write a function to calculate the difference between the lowest and highest value for an array of integers. Return the difference as the result. 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([10, 0, 20, 30, -5])==35
  assert diffHighestLowest([])==0
  assert diffHighestLowest([42])==0
  assert diffHighestLowest([-7, -3, -10, -2])==8
output: def diffHighestLowest(arr):
      if not arr:
          return 0
      lowest = min(arr)
      highest = max(arr)
      return highest - lowest