When it comes to data structures, linked lists are a frequent topic in technical interviews. If you’re preparing for coding interviews at tech giants like Amazon, Google, or startups, mastering linked list interview questions is essential.
In this blog, we dive deep into Linked List Interview Questions and Answers, covering everything from basics to advanced topics.
📌 People Also Ask:
👉 What are the 4 types of linked list?
The four main types are:
- Singly Linked List: Each node points to the next node.
- Doubly Linked List: Each node points to both next and previous nodes.
- Circular Linked List: Last node points back to the first node.
- Circular Doubly Linked List: Doubly linked and circular.
👉 Is a linked list asked in interviews?
Yes, linked lists are a very common interview topic to test a candidate’s understanding of data structure fundamentals, memory management, and pointer manipulation.
👉 What is the main purpose of a linked list?
A linked list efficiently manages dynamic memory, allowing insertion and deletion operations without reallocation, unlike arrays.
👉 How to solve linked list problem?
Understand the structure, manage pointers carefully, and think recursively or iteratively depending on the situation. Visualization and dry runs help significantly.
✨ Top Linked List Interview Questions and Answers
1. What is a Linked List?
A Linked List is a linear data structure where elements are stored in nodes, with each node pointing to the next node.
2. What are the different types of Linked Lists?
- Singly Linked List
- Doubly Linked List
- Circular Linked List
- Circular Doubly Linked List
3. What are the advantages of linked list over arrays?
- Dynamic size
- Easy insertion/deletion without memory reallocation
4. What are the disadvantages of linked lists?
- More memory usage (pointers)
- No random access, slower traversal
5. What is a Singly Linked List?
A singly linked list contains nodes where each node has data and a pointer to the next node.
6. What is a Doubly Linked List?
Each node contains data, a pointer to the next node, and a pointer to the previous node.
7. What is a Circular Linked List?
The last node of the list points back to the first node instead of pointing to null.
8. How do you reverse a linked list?
Iteratively change the next pointer of each node to point to the previous node.
9. How to detect a loop in a linked list?
Using Floyd’s Cycle-Finding Algorithm (slow and fast pointers).
10. How to find the middle element of a linked list?
Use two pointers: slow advances one node, fast advances two nodes.
11. How do you remove duplicates from an unsorted linked list?
Use a HashSet to keep track of seen values.
12. How to check if two linked lists intersect?
Find lengths, align pointers and then check for a common node.
13. What is the time complexity of inserting a node at the beginning?
O(1)
14. How to merge two sorted linked lists?
Use a dummy node and build the merged list by comparing nodes.
15. How to detect and remove a loop in a linked list?
First detect using Floyd’s Algorithm, then fix by moving pointers.
16. What is a dummy node in linked list problems?
A placeholder node used to simplify edge cases like inserting/deleting at the head.
17. What is a sentinel node?
A special dummy node that makes implementation cleaner by eliminating special cases.
18. How do you delete a node without head pointer?
Copy the next node’s data to the current node and delete the next node.
19. How do you find the nth node from the end?
Use two pointers, move one ahead by n steps, then move both together.
20. What is a skip list?
A layered linked list allowing fast search, insertion, and deletion (used in databases).
21. How to find the length of a linked list?
Traverse and count the nodes.
22. What is a circular doubly linked list?
A doubly linked list where the last node connects back to the first node.
23. Can we implement a stack using a linked list?
Yes, by pushing and popping at the head (O(1)).
24. Can we implement a queue using a linked list?
Yes, by enqueuing at the tail and dequeuing at the head.
25. What are real-world applications of linked lists?
- Music playlist
- Web browsers’ history
- Image viewer
- Hash maps (for collision handling)
26. What causes memory leak in linked list operations?
Not properly freeing memory when nodes are deleted.
27. How do you free a linked list in C/C++?
Traverse and delete each node individually.
28. Can linked lists be circular and singly linked at the same time?
Yes, when the last node points to the head.
29. How can you clone a linked list with random pointers?
Use hash mapping or a space-efficient interleaving method.
30. What is difference between singly and doubly linked list?
Doubly has two pointers (next and prev), singly has one (next only).
31. How do you insert a node at a given position?
Traverse to the previous node, adjust pointers.
32. How to sort a linked list?
Use Merge Sort for efficient O(n log n) sorting.
33. What happens if you forget to update next pointer?
You may lose part of the list leading to memory leaks.
34. Is Linked List memory efficient?
It is efficient for dynamic memory usage but uses extra space for pointers.
35. Which sorting algorithms are best for linked lists?
- Merge Sort
- Insertion Sort
36. How can a linked list be used to implement polynomial addition?
Each node represents a term with a coefficient and exponent.
37. What is multilevel linked list?
A linked list where each node can have multiple next pointers (hierarchical structures).
38. How is linked list used in graph representations?
Using adjacency lists.
39. How to flatten a multilevel linked list?
Use recursion or stack to rearrange pointers.
40. What is a NULL pointer in linked list?
Indicates the end of the list.
41. What are common mistakes with linked lists?
- Not handling empty list
- Losing track of head or tail
- Incorrect pointer updates
42. What is tail recursion in linked lists?
When recursive call is the last operation, enabling optimizations.
43. How is garbage collection handled for linked lists in Java?
Automatically via JVM’s garbage collector.
44. What is memory fragmentation in linked lists?
Scattered nodes in heap memory causing inefficient access.
45. Why might linked list access be slower than arrays?
No contiguous memory, hence poor cache performance.
46. How to reverse a doubly linked list?
Swap next and previous pointers at each node.
47. How to detect palindrome in linked list?
Reverse second half and compare with the first half.
48. What is the difference between deep copy and shallow copy of linked lists?
Deep: Copies nodes individually.
Shallow: Copies reference.
49. What is dummy head in linked list?
Fake head node simplifying operations like insert/delete.
50. Can linked lists store different data types?
Generic linked lists can, but typically nodes have uniform data types.
📈 Final Words
Linked List Interview Questions are crucial for cracking coding interviews.
Understanding concepts like pointer manipulation, recursion, and memory management is key to solving linked list problems effectively.
✅ Practice more, dry-run your solutions, and visualize node connections.
✅ Mastering linked lists will build a strong foundation for trees, graphs, and complex data structures!