Top 10 Data Structures & Algorithm Interview Questions & Answers

You may often wonder, what kind of questions will you face in a data structure interview? In these types of discussions, interviewers don’t expect perfection or don’t want to mislead you in any way. All they do is ascertain your knowledge before they invest in your employment. Hence, if you’re well prepared, you’ll impress your interviewers easily and increase your chances of getting hired. 

Algorithm and data structures questions are essential parts of interviews for approximately all programming jobs, especially for Data Science or Java-based roles. Possessing sound knowledge of data structures and algorithms helps make candidates outshine the crowd. Here are the top ten data structure and algorithm interview questions to help you nail your upcoming interview!

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1. What do you mean by Data Structure?

Data structure refers to how data is stored and organized. It involves the process of manipulating the stored data for retrieval as well as access. Moreover, data structure defines how different sets of stored data relate by establishing other relationships and forming algorithms.

2. What are the different types of Data Structures?

The following are five different subtypes of data structures:

• Lists: This is a collection of several related things linked to the previous items or even the following data items.
• Arrays: This is a collection of different values that are all equivalent.
• Records: This collection of data fields, each of which has data sourced from a single data prototype.
• Trees: This type of data structure is organized, and here, the data is structured in a hierarchical framework. This data structure has a fixed order of data items to be inserted, deleted, and modified.
• Tables: Herein, the data is saved as columns and rows. These are similar to the records where the alteration or outcome of information is mirrored across the entire table.

3. What do you mean by Linear Data Structures? List a few examples of the same:

Data structures can be called linear if all the elements or data-based items are structured in an upward sequence or a linear order. The elements are arranged in a non-hierarchical method so that every data prototype has predecessors and successors except the first and last data listed in the sequence.

Some famous examples of linear data structures include stacks, arrays, strings, linked lists, and queues.

4. Give examples of how data structures can be used primarily?

Data structures are primarily used in understanding operating systems, numerical analysis, AI handling, compiler designing, database management, statistical analysis, graphics, and simulation of the stored data.

5. How is a file structure different from a storage structure?

The main difference between the two lies in the accessible memory area. Storage structure means all the data structures in a computer system’s memory. On the other hand, a file structure refers to the storage structure in the auxiliary memory.

6. What do you mean by multidimensional arrays?

Multidimensional arrays have more than one dimension. These are arrays that have numerous layers. The two-dimensional or 2D display is the most commonly occurring multidimensional array. A 2D array is also called a matrix or a table with columns and rows. Other multidimensional arrays are also similarly structured. 

7. In what ways are the elements of a 2D array stored in a computer’s memory?

2D arrays are stored in the following ways:

Row Major Order: -In row-major order, all the rows of any 2D array are arranged in the memory in contiguous manners.

Column Major Order: In a column-major order, all the columns of 2D arrays are stored in the memory at the same level. Similar to the row order, the first column is also entirely saved into the computer’s memory, followed by the second and the subsequent columns until the last column is entirely saved.

8. What do we mean by a linked list data structure?

This question is one of the most commonly asked data structure and algorithm interview questions. 

The linked list data structure is a linear data structure with a sequential arrangement of data where the elements are not structured in any adjacent memory locations. Instead, these elements are linked by pointers to create a chain. Each element is a separate item, called nodes.  Each of these nodes has two individual items: 

• A data field that is about the next node. 
• The entry point of a linked list is called the head. 
• Where such a list is empty, the head of the data structure works as a null reference.

A linked list is a dynamic data structure. Here, the number of nodes isn’t fixed, and this list also can shrink or grow on demand.

9. Are linked lists considered linear or non-linear as data structures?

Linked lists of data are considered both linear and non-linear in data structures. However, this also depends upon which application they are used for. If used for access strategies, linked lists are considered linear data structures. If used for simple data storage, they are deemed non-linear data structures.

10. What are the main benefits of using a linked list over a multidimensional array? 

This is yet another frequently asked algorithm and data structure interview question! The main Advantages of using a linked list over a multidimensional array are:

• Deletion and insertion

When using a linked list data structure, inserting and deleting nodes is a much easier process. This is because, in a linked list, we only update the main address present in the subsequent pointer of the first node. On the other hand, it’s relatively expensive to do the same in a multidimensional array because a separate room is needed for all the new elements and even for storing the existing elements, which must be shifted.

• The dynamic structure of data 

As a linked list structure is a unique data structure, there is no compelling reason to give an underlying size. It can develop and contract at runtime by distributing and deallocating memory. In any case, the size is restricted in an exhibit as the number of components is statically put away in the primary memory.

• Memory isn’t wasted

Because the size of a linked list can shrink or grow as needed, no memory is wasted. Also, in a linked list, memory is allocated as and when required, leading to minimal memory wastage. However, for multidimensional arrays, there is significant memory wastage. 

• Implementation

Data structures in linked lists such as queues or stacks are easily implemented using a linked list rather than an array.

The Bottom Line 

These data structure interview questions must have given you an insight into the type of questions that interviews could ask you. Many of the data mentioned above structure interview questions as a sure-shot entry in an interview. Hence, make sure to brush up on your data structures and algorithm knowledge. If you possess a comprehensive understanding of these basic data structures and how to access data elements from arrays or linked lists, you’ll be good to go!

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