Top Data Structure Interview Questions: For Freshers

Blog
webiamneo@gmail.com

Proficiency in Data Structures is a must-have for any well-qualified software developer. Most of the product-based companies search for candidates with a strong understanding of Data Structures, since it is the building block to develop any software. The need for Data Structures is at an all-time high, as it has become inevitable in almost all industries. Hence to ace your interviews easily, you must know these top DSA questions.

For an exploring fresher, we recommend you to have knowledge on the top demand jobs of this decade to make yourself prepared.

What are Data Structures?

There are various types of data such as integer, character, string, boolean, enum and array. The computer interprets a value based on the datatype in which it is stored.

Once the data is stored, we need a way to manipulate it to solve the problems. Data Structures is a format that helps to store and organize data in an efficient way. This helps to increase the overall code performance by establishing relationships among the data sets. Arrays, linked lists, stacks, queues, trees and graphs are some of the data structure types.

Data Structures Interview Questions

Now let us take a look at some of the important data structure questions that will be asked in any interview.

1. List some of the applications of Data Structures

Data structures aid in managing, accessing, and manipulating large amounts of information. In this data-centric world, they are essential in nearly all industries. Some of the key areas where they are utilized include:

  • Blockchain
  • OS Development
  • Database Design
  • Complier Design
  • Machine Learning
  • Financial Systems
  • Image Processing
  • Video Games
  • Web Search Engines
  • Artificial Intelligence

2. How do you categorize linear and non-linear data structures?

In a linear data structure, the data elements are arranged in a sequential manner. One data element will be connected to its previous and/or next element in a linear fashion. There are no multiple relationships between elements and hence the traversal through data can be carried out only in a single run.

Array, queue, linked list and stack are some of the examples of a linear data structure.

Non-linear data structures are the opposite of what we said about linear data structures. The elements are connected in a hierarchical manner and hence their implementation is more complex. There is no memory wastage here.

Graphs and trees are non-linear data structures.

3. What is the difference between file structure and storage structure?

File Structure: A file structure representation is the process of converting data into a form that can be stored in a secondary memory device such as a hard disk or a pen drive. The stored data remains unchanged until it is manually deleted.

Storage Structure: Storage structure stores the data in computer memory that is, RAM. It is not permanent and gets erased as the function that uses this data executes.

4. What are the operations that can be performed on data structure types?

Traversing: Visiting the elements of data structure in a systematic manner.

Searching: Locating the required element in the data structure.

Inserting: Adding an element anywhere inside the data structure. In stack, it is called push and in queue it is called enqueue.

Deleting: Removing an element from the given data structure. In stack, it is called pop and in queue it is called dequeue.

Sorting: Arranging elements of a data structure in ascending or descending order.

Updating: Updating the value or replace an element in a data structure.

5. What is a linked list?

A linked list is a linear data structure in which each element, called a node, contains a reference (or “link”) to the next node in the sequence. The last node in the linked list typically has a link to null, indicating the end of the list.

Linked lists have several advantages over arrays, including dynamic sizing and efficient insertions and deletions. Linked lists can also be easily implemented in a variety of programming languages, making them a common data structure for a wide range of applications.

6. What are the types of linked lists?

Singly Linked Lists – each node contains a reference to the next node

Doubly Linked Lists – each node contains references to both the next and previous nodes.

Circular Linked Lists – the last node contains a reference to the first node

7. How linked lists differ from arrays?

ArrayLinked List
StructureElements are stored in consecutive memory locations.Collection of nodes, where each node contains a reference (or “link”) to the next node in the sequence
Access TimeConstant time complexity of O(1) to access an element.Time complexity of O(n) for searching elements.
SizeHave a fixed size, determined at the time of allocation.Grows dynamically as elements are added or removed.
Insertion/DeletionTime consuming as it requires shifting all the elements after the insertion/deletion point.Average time complexity of O(1) for inserting and deleting elements, as only the links between the nodes need to be updated.
Memory utilizationIneffective as we allocate the size during declarationEffective as the size adapts during runtime

8. When do we use linked list?

We use linked lists when

  • The size of data is not known in advance
  • Faster insertion and deletion are required
  • Less number of random-access operations are involved
  • There is a large number of add or remove operations
  • We have to perform arithmetic operations on long integers
  • We need to manipulate polynomials

9. How do stack and queue work?

A stack is a linear data structure in which elements can be added or removed only from the top. A stack follows the LIFO – Last In First Out principle meaning, the element that was added last is the first to come out.

A queue is a linear data structure in which elements can be inserted only from the rear, and can be removed only from the front. A queue follows the FIFO – First In First Out principle meaning, the element inserted at first is the first to be removed.

10. Where do we see stack and queue in real life?

Stack in real life:

  1. Pile of Books
  2. Women’s Bangles
  3. Floors in a Building
  4. Stack of Plates in a cupboard
  5. Cars parked in a narrow driveway

Queue in real life:

  1. Waiting line
  2. Car wash line
  3. Vehicles in a Traffic Signal
  4. People in an escalator

11. Explain hashmap data structure

A Hash Map (also known as Hash Table) is a data structure that allows you to store key-value pairs and efficiently retrieve the value associated with a given key. A real-world example for hashmap would be when you store your bags in a cloak room and get a token for the spot where you have stored. You will be able to retrieve your baggage only using the token.

Conclusion

There goes the top data structure questions and answers to ace your interview. Sandbox Environments are an ideal place to start practicing what you have learnt. If you are learning on your own, you can use an auto-evaluation supported sandbox like neocoder.