1. Linked List Interview Prep
Spencer Moran
11/20/13

2. Why Linked Lists?
• Simplicity
• Little variation
• Pointers and references

3. Singly Linked List
Almost all LL interview questions are based on singly linked lists

4. Doubly Linked List

5. Implementation
• Can be implemented as
an ADT
• Often use templates
• List is referred to by the
head, the first node in
the list
• If you modify the
list, you must return the
head of the new list

6. Traversal

7. Insertion

8. Deletion

9. Linked List Question Strategies
• Use two (or more??) pointers to traverse the
list
• Traverse pointers at different speeds
• Use an additional data structure

10. Common Linked List Questions
Find the kth to last element in a singly linked list.

11. Strategy
• Use multiple pointers to traverse the list.
• Return an error if the list is not at least k
nodes long.
• Traverse the list with 2 pointers:
– Pointer1 starts at head
– Pointer2 starts k nodes in front of the head.
– When pointer2 reaches the end of the list, return
pointer1

13. Common Linked List Questions
Determine if a singly linked list has a loop or cycle.

14. Strategy
• Use multiple pointers and traverse them at
different speeds.
• Start both pointers at head:
– Traverse the list, moving fast pointer twice as fast
as the slow pointer.
– If fast pointer reaches the end of the list, there is
no cycle.
– If the pointers ever are equal to one
another, there is a cycle.

16. BONUS QUESTION
Determine if a linked list has a cycle. If it
does, return the element where the cycle
begins.

18. Bonus Question #2
Find the length of the cycle without traversing it
multiple times.

19. Common Linked List Questions
Reverse a singly linked list.

20. Strategy
• Use an additional data structure.
• Traverse the list, pushing each node into the
stack.
• Set the new head equal to the first element in
the list.
• Starting at the new head, add the top element
from the stack until the stack is empty.

22. Other common questions
• Remove duplicates from a singly linked list
• Merge sort
• Remove element from middle of list (without
head)
• Check if the linked list is a palindrome
• Fold a singly linked list using no containers

23. Meeting Summary
We also covered a bunch of questions at the end
of the meeting. These questions were mostly
about linked lists, but we also started covering
trees and decided that trees and graphs will be
our next topic. The date of our next meeting will
be arranged through the facebook group.