Top Data Structures Interview Questions & Answers

Programming as a job is a category that has grown manifold times in the past decade. Jobs in this field are increasing with each passing year and it isn't very difficult to grasp programming.

When it comes to the programming field. the favorite questions that interviewers love to ask come from Data Structures & Algorithms. Even though the concepts of DS & Algo isn't very wide, the questions that can be formed from these topics are countless.

Before the technical questions, you must be comfortable in answering the basic questions like- Tell me about yourself, What do you know about the company, Why do you want to join our company, and other such questions. After this comes the questions related to Data Structures,

So in this article, we are going to discuss the important questions on DS that can be asked by the interviewers.

But before jumping to that, let us discuss a brief about Data Structures.

What is Data Structure

In computer science, a data structure is a data organization, management, and storage format that enables efficient access and modification.

More precisely, a data structure is a collection of data values, the relationships among them, and the functions or operations that can be applied to the data.

Data structures provide a means to manage large amounts of data efficiently for uses such as large databases and internet indexing services. Usually, efficient data structures are key to designing efficient algorithms.

Now that we are done discussing the basics, let us move onto the interview questions.

Interview Questions on Data Structures

Q1. Explain the types of Data Structures.
Ans- There are mainly two types of Data Structures:

1. Linear Data Structure: When all of its components are organized in a proper sequence, a data structure is called linear. The components are stored in linear data structures in a non-hierarchical manner where each item has the successors and predecessors except for the first and final element.

2. Non-linear data structure: The Non-linear data structure does not form a series, i.e. each object or entity is linked to two or more than two objects in a non-linear manner. The elements of the data are not organized within the sequential model.

Q2. Discuss the Different Operations that can be Carried out on Data Structures?
Ans- Following are the different operations that are generally carried out in Data Structures:

Insert– Add a new data item in the already existing set of data items.
Delete– Remove an existing data item from the given data item set.
Traverse– Access each piece of data precisely once so that it can be processed.
Search– Figure out where the data item resides in the specified data item set.
Sort– Arrange the data objects in certain order i.e. in ascending or descending order for numerical data and in dictionary order for alphanumeric data.

Q3. Explain the Concept of a Queue. How can you differentiate it from a Stack?
Ans- A queue is a type of linear structure that is used to access components that support the FIFO (First In First Out) method. Dequeue, enqueue, front, and rear are key queue functions. Unlike a stack, the arrays and linked lists are used to enforce a queue.

The element most recently added is removed first in a stack. However, in the event of a queue, the element least recently added is removed first.

Q4. Explain the Steps Involved in the Insertion and Deletion of an Element in the Stack
Ans– Algorithms of Stack operations :

Algorithms of PUSH operations-

Step 1: Start

Step 2: Checks if the stack is full if(top==(SIZE-1))

Step 3: If the stack is full, Give a message and exit printf("\nStack Overflow");

Step 4: If the stack is not full, increment top to point the next empty space.

top=top+1;

Step 5: Add the data element to the stack location, where the top is pointing.

printf("\nEnter the item to be pushed in stack:"); stack[top]=item;

Step 6: Stop

Algorithms of POP operations :

Step 1: Start

Step 2: Checks if the stack is empty if(top==-1)

Step 3: If the stack is empty, Give a message and exit printf(“\nStack Underflow”);

Step 4: If the stack is not empty, Print the element at which the top is pointing.

printf("\nPopped element is : %d\n",stack[top]);

Step 5: Decrement top to point previous location.

top=top-1;

Step 6: Stop

Q5. What is a Binary search?
Ans- A binary search only operates on sorted lists or arrays. This search chooses the middle which divides the whole list into two sections. The middle one is compared first. It works by halving the array on each iteration until the necessary element is found.

Q6. What do you Understand by Array and Multidimensional Array?
Ans- Arrays are characterized as the gathering of similar types of data items stored at contiguous memory locations. It is the simplest data structure that allows random access to any data item by using its index number.

The multidimensional array can be known as the array of arrays which takes the form of rows and columns wherein the data is kept in tabular form.

2D arrays are generated to enforce the lookalike data structure of a relational database. It gives the convenience of carrying a large amount of data at once that can be transferred on to any number of functions where necessary.

Q7. Explain the Process of Hashing
Ans- Hashing is the process of transforming a set of key values into a collection of array indexes. Associative data storage can be generated by hash tables where data indices are identified by supplying the key values that correlate.

Q8. Give names of all the Trees.
Ans- There are six types of trees given as follows.

General Tree
Forests
Binary Search Tree
Tournament Tree
Binary Tree
Expression Tree

Q9. List the area of applications where the stack data structure can be used?
Ans- Areas, where the stack data structures can be used, are

1. Expression evaluation
2. Backtracking
3. Memory Management
4. Function calling and return

Q10. Can you Explain the Difference Between a Linked List and an Array?
Ans- Difference between Linked List and an Array are:

1. Linked List is an ordered collection of elements of the same type in which each element is connected to the next using pointers while Array is a collection of elements of a similar data type.

2. Size of an Array is fixed whereas it isn't fixed in Linked Lost.

3. Memory is allocated from the stack in the linked list whereas it is allocated from the heap in Array.

4. Data cannot be accessed randomly in Linked List whereas it can be accessed randomly in the Array using the array index.

Q11. What is a multidimensional array?
Ans- The multidimensional array can be defined as the array of arrays in which, the data is stored in tabular form consists of rows and columns.

2D arrays are created to implement a relational database lookalike data structure. It provides ease of holding the bulk of data at once which can be passed to any number of functions wherever required.

Q12. What is a doubly-linked list?
Ans- The doubly linked list is a complex type of linked list in which a node contains a pointer to the previous as well as the next node in the sequence. In a doubly-linked list, a node consists of three parts:

1. Node data
2. Pointer to the next node in sequence (next pointer)
3. Pointer to the previous node (previous pointer)

Q13. What is a dequeue?
Ans- Dequeue (also known as a double-ended queue) can be defined as an ordered set of elements in which the insertion and deletion can be performed at both the ends, i.e. front and rear.

Conclusion

These are the most commonly asked questions in interviews. These questions display that you have an understanding of Data structures. If you want to learn in deep about this topic, you could look up tutorials on Youtube like this or use any reference book.

It would be very helpful if you at least brush up these topics and by brushing up, I mean not just memorizing it. It would be better if you understand them by practicing.

Thanks for reading.