input: Write a function to find the difference between the highest and lowest values in a list of integers. If the list 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([]) == 0
  assert diffHighestLowest([5, 5, 5, 5]) == 0
  assert diffHighestLowest([10, -10, 10, -10]) == 20
  assert diffHighestLowest([-10, 0, 10]) == 20
output: def diffHighestLowest(arr):
      if not arr:
          return 0
      lowest = min(arr)
      highest = max(arr)
      return highest - lowest