Output (1), after 4 add_to_back and 2 add_to_front calls:
  12
  24
  8
  24
  16
  35
Output (2), after removing 24:
  12
  8
  16
  35
Output (3), after reverse_list:
  35
  16
  8
  12
Output (4), after destroy_list:
  <empty>
Output (5), after creating an ordered list:
  buffalo
  chimp
  monkey
  monkey
  zebra
Output (6), after merging two ordered lists:
  banana
  buffalo
  chimp
  monkey
  monkey
  monkey
  tiger
  zebra