input: def swap(arr1: List[int], arr2: List[int]):
      """ Replace each element in arr1 with the corresponding element in arr2 and vice versa.
      >>> swap([3, 5, 6, 9], [2, 4, 7, 8])
      ([2, 4, 7, 8], [3, 5, 6, 9])
      >>> swap([1, 1, 1, 1], [2, 2, 2, 2])
      ([2, 2, 2, 2], [1, 1, 1, 1])
      """
output:     for i in range(len(arr1)):
          arr1[i], arr2[i] = arr2[i], arr1[i]
      return arr1, arr2