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Since doubly linked lists have a tail property, we don’t have to iterate through the entire list to add to the tail like we did with a singly linked list. The new method will mirror what we did in our .add_to_head() method:
- Start by checking to see if there is a current tail to the list
- If there is (meaning the list is not empty), then we want to reset the pointers at the tail of the list:
- Set the current tail’s next node to the new tail
- Set the new tail’s previous node to the current tail
- Update the tail property to be the new tail
- Finally, if there isn’t a current head to the list (meaning the list was empty):
- Update the head property to be the new tail since that node will be both the head and tail
Instructions
1.
Define an .add_to_tail() method that takes self and new_value as parameters.
Inside, create:
- A
new_tailNodethat takesnew_valueas a parameter - A
current_tailNodethat’s set to the list’s tail
2.
If there is a current tail to the list:
- Set the current tail’s next node to
new_tail - Set
new_tail‘s previous node to the current tail
3.
Outside your if statement, set the list’s tail to the new_tail.
4.
Lastly, if the list doesn’t have a head, set the list’s head to the new tail.
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