Data Structures and Algorithms Interview Questions for Freshers

As a fresher, to nail your coding interviews and perfect your software projects, you’ll be needing the help of data structures and algorithms interview questions for freshers.

These questions are one of the most efficient ways to make your software hit aces when it comes to performance.

We know that this topic is taught in almost every IT university. However, students generally fail to understand these concepts at that time. It’s only realized after they’ve set foot in the software industry – which is too late!

Therefore, I decided to share with you all the data structures and algorithms interview questions for freshers so that you have all that is required to crack your technical interviews.

Please note, if you are not a fresher then I have already written about Data Structures and Algorithms Interview Questions for Experienced.

Importance of Data Structures and Algorithms

It is such an important topic that most interviewers throw questions from data structures and algorithms to test developers. They’ll ask you questions and keep building a chain from the answers you give – expertise is a must-have!

If you do not know about these topics and data structures and algorithms questions for freshers, you may not be able to write efficient code to handle your projects. Neither will you be able to answer the questions your interviewer might ask.

If you are a fresh graduate or beginner, you must be thinking:

What are the data structures and algorithms interview questions for freshers that interviewers ask? How am I going to tackle those questions?

Whether you’re a fresher or a developer who has just graduated, I’ve got your back.

This article has everything you’ll need for your learning – books on data structures and algorithms, credible sources for interview questions, and their answers as well. Also, I’ll try to reference some of those interview questions here so you can get started properly.

However, these data structures and algorithms interview questions will be for fresh programmers and beginners specifically. Some multiple-choice questions and lab practical questions and answers of data structures and algorithms may help you too. 

Learning Data Structures and Algorithms: Getting Started

First, have a look at some essential data structures and algorithms. If you are new to the programming world, you might have trouble getting equipped with the topics at hand.

Without having a good grasp on these topics, you are not going to ace your coding interview. That said, here’s a list of some of the most important data structures you’ll come across in your coding interviews as a fresher:

Important Data Structures for Interview

  • Arrays, stacks, and queues (basic data structures)
  • Linked lists (customized arrays)
  • String (array data structure of words)
  • Trees and graphs (complicated data structures)

Similarly, you’ll also be needing some expertise in algorithms. Here’s a list of some of the most common algorithms which interviews love to test candidates on:

Important Algorithms for Interview

  • Sorting algorithms
  • Searching algorithms
  • Hashing
  • Dynamic programming
  • String matching and parsing
  • Graphs algorithms

Books to Learn Data Structures and Algorithms

Next, let’s have a look at some of the best books on data structures and algorithms. Here’s a list of the books you’d love to read on these concepts

Dynamic Data Structures: Lists, Stacks, Queues, and Trees

Dynamic Data Structures

Author: Bogdan Patrut, Tiberiu Socaciu
Description: This book will help you to understand the difference between static and dynamic variables. Also, you can learn the role of pointers, which are vital in languages like C and C++. You will also learn different types of data structures such as stack, queue, double-linked list, circular list, and binary tree. After learning these concepts, you can solve exercises to increase your understanding.

C++ Programming: Program Design Including Data Structures (6th Edition)

C Programming DS Malik

Author: D.S Malik
Description: This will help you learn data structures and algorithms in C++ specifically. It is the best book, in my opinion, and can help you build a better understanding. This book will help you in understanding almost all the concepts of data structures and algorithms in programming language C++.

Data Structures And Algorithms In Java  (2nd Edition)

DSA Robert Lafore

Author: Robert Lafore
Description: If you are learning data structures and algorithms in Java, then this book will surely help you out. Beginners and professionals both can study via this coursebook for improving skills. The concepts in this book will help you, especially with the graphical demonstration of how data structures look like and how they operate.

Data Structures and Algorithms in Python

DSA Python

Author: Michael T.Goodrich
Description: This textbook offers a comprehensive and definitive introduction to data structures in Python. The book also provides an in-depth introduction to a variety of algorithms and data structures that are used by industry professionals, including their design, analysis, and implementation. You’ll have a better understanding after completing these books.

Data Structures and Algorithms Interview Questions for Freshers

Let’s have a look at some of the most common interview questions for freshers. I’ll take you through some data structure questions and then discuss algorithms as well. Here’s a list for you to view.

Basic Data Structures Interview Questions For Freshers

  1. What is the data structure?
  2. What are some areas of application of data structure?
  3. What are the types of data structures?
  4. What are linear and non-linear data structures?
  5. What factors determine the choice of a data structure for a program?
  6. What is the difference between a data type and data structure?
  7. What are data structure operations?
  8. What is a linked list?
  9. What is a binary tree?
  10. What is the queue?
  11. What is a spanning tree?
  12. What is precision?
  13. What are the goals of data structures?

These questions are fairly basics and don’t dig deep into these data structures. Instead, these questions are only focused on “what” these structures are. However, if you’re having trouble answering them, here’s a resource that can help you out: here.

Basic Algorithms Questions for Freshers

  1. What are the Divide and Conquer algorithm? Describe how do they work. Can you give any examples of the types of problems and where this approach might be used?
  2. Can you explain a Binary Search Algorithm? (in C++, Java or Python – mostly write their pseudocode)
  3. How do Insertion sort, Heapsort, Quicksort, and Merge sort work?
  4. What is the difference between a stable and unstable sorting algorithm?
  5. What are the key advantages of Insertion Sort, Quicksort, Heapsort, and Merge sort?
  6. What is a Hash Table?
  7. How would you describe dynamic programming?
  8. What are the Red-Black Trees and B-Trees?
  9. What are the Dijkstra and Prim algorithms?
  10. What is the Bellman-Ford Algorithm for finding single-source shortest paths?
  11. What is basic dynamic programming?
  12. Is it possible to use binary or any other search for linked lists?
  13. Mention what the types of Notation used for Time Complexity are?

These questions are suited for freshers as well. I’ve compiled this list from research and from several credible sources for interviews for software developers. You can find the answers to these questions at this link.

Data Structure Multiple Choice Questions and Answers

Following multiple-choice questions of data structures and algorithms can give you an idea about the questions and their answers. You can judge or self-assess your skills based on that. These questions are mostly asked in the interviewer for freshers to get them started.

Q 1 – What is the worst-case time complexity of the linear search algorithm?

  1. Ο(1)
  2. Ο(n)
  3. Ο(log n)
  4. Ο(n2)

Q 2 – push() and pop() functions are found in

  1. queues
  2. lists
  3. stacks
  4. trees

Q 3 – The following formula is of
=> left_subtree (keys)  ≤  node (key)  ≤  right_subtree (keys)

  1. Binary Tree
  2. Complete Binary Tree
  3. Binary Search Tree
  4. All of the above

Q 4 – What could be the worst-case height of an AVL tree?

  1. 0.97 log n
  2. 2.13 log n
  3. 1.44 log n
  4. n2 log n

Q 5 – Which of the following has search efficiency of Ο(1) –

  1. Tree
  2. Heap
  3. Hash Table
  4. Linked-List

Q 6 – The number of binary trees with three nodes which when traversed in post-order, gives the sequence A, B, C is?

  1. 3
  2. 4
  3. 5
  4. 6

Q 7 – Which of the following uses memoization?

  1. Greedy approach
  2. Divide and conquer approach
  3. Dynamic programming approach
  4. None of the above!

Q 8 – In C programming, when we remove an item from the bottom of the stack, then

  1. The stack will fall.
  2. Stack will rearranged items.
  3. It will convert to LIFO
  4. This operation is not allowed.

Q 9 – The following sorting algorithms maintain two sub-lists, one sorted and one to be sorted

  1. Selection Sort
  2. Insertion Sort
  3. Merge Sort
  4. Both A & B

Q 10 – Interpolation search is an improved variant of binary search. This search algorithm must work that.

  1. data collection is sorted and equally distributed.
  2. data collection is , but not equally distributed.
  3. data collection should be equally distributed but not sorted.
  4. None of the above.

Data Structures Lab Practical Questions

Most interviewers don’t settle with interviews consisting of questions only. They’d probably ask you to implement the solution on paper or on the computer so they can assess your skills. Here’s a list of the most common practical questions you might be asked:

  1. Write code to implement Level Order Search in a Binary Tree?
  2. How is an iterative quicksort algorithm implemented?
  3. How do you swap two numbers without using the third variable?
  4. Write the Algorithm to check if two rectangles overlap with each other?
  5. Implement the QuickSort Algorithm in your Favorite Programing language?
  6. Write more about the array merge-sort Algorithm. Assume that a merging algorithm is already available.
  7. Compare the quick-sort and merge-sort algorithms in terms of their time and space complexity. Which is better in terms of time and space complexity?
  8. Suppose that we start with an empty map, represented by a Binary Search Tree. Then we add (“Homer”, 20000), then add (“Monty”, 500000), then add (“Carl”, 100000), then add (“Lenny”, 25000), then remove “Homer”. Show the contents of the BST after each operation.
  9. Implement Sieve of Eratosthenes Algorithms for Prime Number?
  10. Write a code to reverse a queue?

Congrats! You are ready for your next interview

That’s it for today, folks. I’ll be concluding my article on the most common data structures and algorithms interview questions for freshers. I’ve linked several resources along with the questions you might be asked by interviewers. Here are some really good interview preparation tools:

Make sure you’re following a proper guideline to study from these resources. Start off with data structures and then move on to algorithms. You can also organize them from basic to more complex concepts.

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