20+ Linked List Interview Questions for Java Programmers

Recently, I've been sharing a lot of coding interview questions for those actively seeking jobs as Java developers, particularly beginners, junior developers, and computer engineers who just graduated with no real job experience.

Today, I am going to share a list of frequently asked linked list problems common in coding interviews.

Data structures are one of the most important parts of any programming interview and often are the reason for selecting or rejecting a candidate. That's why reviewing and practicing these data-structure-based problems will give you an edge over your competitor.

It will also make you a better programmer because you develop logic and coding sense while solving these problems, which goes a long way in your programming career.

What Is a Linked List?

A linked list is another common data structure that complements the array data structure. Similar to the array, it is also a linear data structure and stores elements in a linear fashion.

However, unlike the array, it doesn't store them in contiguous locations; instead, they are scattered everywhere in memory, which is connected to each other using nodes.

A linked list is nothing but a list of nodes where each node contains the value stored and the address of the next node.

Because of this structure, it's easy to add and remove elements in a linked list, as you just need to change the link instead of creating the array, but the search is difficult and often requires O(n) time to find an element in the singly linked list.

This article provides more information on the difference between an array and linked list data structures.

It also comes in varieties like a singly linked list, which allow you to traverse in one direction (forward or reverse); a doubly-linked list, which allows you to traverse in both directions (forward and backward); and finally, the circular linked list, which forms a circle.

How to Solve Linked-List Coding Problems in Interviews?

In order to solve linked list-based questions, a good knowledge of recursion is important, because a linked list is a recursive data structure.

If you take one node from a linked list, the remaining data structure is still a linked list, and because of that, many linked list problems have simpler recursive solutions than iterative ones.

They are also solved using divide-and-conquer techniques, which breaks the problem into sub-problems until you can solve them.

For example, to reverse a linked list, you break linked list until you have got just one node. At that point, you know how to reverse that linked list of one node; it's nothing but the same node.

It's very similar to recursion and actually, that smallest sub-problem you can solve becomes the base case for recursive solutions.

Keep in mind: There is no point solving these linked-list-based coding problems if you don't have basic knowledge of data structure or you have not to refresh them in recent time. In that case, I suggest you to first go through a good data structure and algorithm courses or book to revise the concept.

Top 20 Linked-List Problems In Java Interviews

Without wasting any more of your time, here are some of the most common and popular linked list interview questions from Coding interviews. I have linked to the solution wherever possible but I suggest you first try to solve the problem on your own, that will benefit you because you will think and learn.

Once you have solved the problem or stuck after trying, you can look at the solution and learn from them.

1. How do you find the middle element of a singly linked list in one pass? (solution)
2. How do you reverse a singly linked list without recursion? (solution)
3. How are duplicate nodes removed in an unsorted linked list? (solution)
4. How do you find the length of a singly linked list? (solution)
5. How do you check if a given linked list contains a cycle? How do you find the starting node of the cycle? (solution)
6. How do you reverse a linked list? (solution)
7. How do you find the third node from the end in a singly linked list? (solution)
8. How do you find the sum of two linked lists using Stack? (solution)
9. How do you reverse a linked list in place? (solution:
   (http://www.java67.com/2017/06/5-difference-between-array-and-linked.html)**
10. How to remove Nth Node from the end of a linked list? (solution)
11. How to merge two sorted linked list? 
12. How to add an element at the middle of the linked list? 
13. How do you sort a linked list in Java? (solution)
14. What is the difference between array and linked list? 
15. How to convert a sorted list to a binary search tree? (solution)
16. Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x. (solution)
17. How to remove all elements from a linked list of integers which matches with given value? 
18. How to find the node at which the intersection of two singly linked lists begins. (solution)
19. How to check if a given linked list is a palindrome? 
20. How to remove duplicates from a sorted linked list? (solution)

These questions will help you to develop your problem-solving skills as well as improve your knowledge of the linked list data structure.

Useful Resources for Programming Interviews

If you need some useful resources to do well on your programming and coding job interview, here are some of the online courses and books you should check out:

1. Data Structures and Algorithms: Deep Dive Using Java
2. Grokking the Coding Interview: Patterns for Coding Questions
3. Cracking the Coding Interview Book
4. Master the Coding Interview: Data Structures + Algorithms
5. Preparing For a Job Interview By John Sonmez

I have shared a lot of resource in this article or Java, Python, and C++ developers to learn data structure and algorithms. Some of these resources are free and some of them are paid, for paid ones I'll get paid if you buy them using links in this article, but only buy them if you really need them and only after watching previews and reading sample chapters. They are the best resource but its important for you to connect to the author or instructor to get the most of them, hence buy the resource on which you connect with them.

Congrats! You're One Step Closer to Preparing For Your Coding Interview

These are some of the most common questions outside of data structure and algorithms that help you to do really well in your interview.

These common coding, data structure, and algorithms question*s* are the ones you need to know to successfully interview with any company, big or small, for any level of programming job.

If you are looking for a Java, Python, or C++ Programming and software development job in 2019, you can start your preparation with this list of coding questions.

This list provides good topics to prepare and also helps assess your preparation to find out your areas of strength and weakness.

Good knowledge of data structure and algorithms is important for success in coding interviews and that's where you should focus most of your attention.

Thanks, You made it to the end of the article ... Good luck with your programming interview! It's certainly not going to be easy, but you are one step closer to the success and the job you always wanted, after practicing these questions.