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([3, 5, 10, 14, -2])==16
  assert diffHighestLowest([4, 3, 1, 2])==3
  assert diffHighestLowest([3, 5, 4, 1, 2])==4
  assert diffHighestLowest([])==0
output: def diffHighestLowest(arr):
      if not arr:
          return 0
      lowest = min(arr)
      highest = max(arr)
      return highest - lowest