# 20 Data Structures Interview Questions and Answers

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Understanding data structures puts one a step closer to designing efficient algorithms in programming. We are here to give you the basic knowledge on the subject through the top 20 data structures interview questions and answers discussed in this article. The interviewers often don?t look at how sophisticated your knowledge is but rather how well you have interacted with the topic. Therefore, here are some of the data structures interview questions that they may randomly throw at you, and their most appropriate answers.

## Question 1: What are data structures?

Of all the data structures interview questions, that is definitely the most obvious question to expect.
Data structures are ways of defining, storing and retrieving information in a systematic and organized way. It not only considers the data items stored but their structural relationships with each other.

## Question 2: What is the difference between a file structure and a storage structure?

The main point of distinction between the two is the memory area that has to be accessed. Storage structure has to do with the structure that resides in the main memory while file structure involves the supporting structures for data storage.

## Question 3: What is binary search and when do we apply it?

A binary search is an algorithm used to find a list when the elements have been sorted or arranged in order. It is considered that the search in the list is initiated from the middle such that if the middle value isn?t the target, then it continues to the bottom half or top half. The split search is way faster.

## Question 4: What is the goal of a data structure?

The data structure at the end of the organization should be rich enough such that it clearly reflects the relationships of the data items in real life. The structure should be too complex that data processing is slackened.

## Question 5: Explain how you can find the element of linked list in a single pass.

This process can be easily accomplished in one pass by first maintaining a two-pointer. Ensure that there is a single increment at each of the nodes and the other increments after two nodes at a time. You will notice that when the first pointer reaches the end, the second pointer will be at the center element of the linked list.

## Question 6: What are the sectors in which data structures are extensively applied?

Data structures are widely used in the following sectors:

• Database management systems DBMS;
• Operating systems;
• Artificial intelligence;
• Numerical analysis;
• Compiler design;
• Simulation;
• Graphics;
• Statistical analysis package.

## Question 7: Define an algorithm.

An algorithm is a step-wise laid down procedure defining a set of instructions that need to be executed in a given order for a desired result or output.

## Question 8: What is the essence of algorithm analysis?

Usually, there are myriads of ways to solve problems. Therefore, with an algorithm, we can explore these ways by designing many solution algorithms. After that, the algorithms can be analyzed individually and the best ones that provide solutions to the problem singled out.

## Question 9: How can one reference the entire elements in a single-dimension array?

An indexed loop can be employed to accomplish that task, whereby the counter goes from zero to the final value of the array less one. Most interviewers would be satisfied with this answer. However, if they insist, you could also mention that this procedure allows us to reference all of the elements by making the loop counter the array?s lower index. this is one of the trickiest data structures interview questions.

## Question 10: What do you understand by LIFO?

It is a contracted form of Last in First Out which is a tool for data access, storage and retrieval in a data structure. This principle implies that the data that was stored last should be obtained first.

## Question 11: What is the meaning of Abstract Data Type?

A data type is a combination of values and the possible collection of operations on the values themselves. Therefore, an abstract data type refers to the mathematical concept behind the data type, and it exists in two forms:

• Value definition;
• Operation definition.

## Question 12: Differentiate between a Stack and an Array.

A stack is a dynamic collection of data items in a particular order whereas an array is a static, ordered collection of data items. The size of the stack changes as objects increases upwards while in an array, the number of the items is fixed.
Another difference is that the stack can contain different data types while the array usually contains the same data types.
The stack is often declared as a structure that contains an array to hold its element while an array can be considered a home of a stack. Arrays are declared as big as possible to accommodate the size of the stack.

## Question 13: When performing a recursion, what data structure can you use?

The stack would be most appropriate because it has the Last-in-First-Out property. This way, it will tell which caller to return to when the operation has to return. Recursion utilizes the system stack for the storage of the return addresses of the called functions. Every recursive function has its non-recursive or iterative counterpart, where in both cases an explicit stack is employed.

## Question 14: Explain the asymptotic analysis of an algorithm.

This is another common issue among the data structures interview questions.
It refers to the definition of a mathematical framing of the algorithm?s runtime performance. This analysis method brings out the best, average and worst case scenarios for a given algorithm.

## Question 15: Define a linear data structure.

It is a sequential arrangement of the data items. Each item is allocated memory in its address in a sequential manner.

## Question 16: What is the role of allocation of dynamic memory in data management?

They have the capability to store simple structured data types. In addition to that, they can combine allocated structured data blocks separately such that they form compound structures which can be expanded and contracted as required.

## Question 17: What is the difference between NULL and VOID?

NULL is a value while VOID is a tool for identifying a data type. The former shows an empty value while the latter identifies pointers that lack initial size.

## Question 18: What is the major advantage of a linked list?

A linked list is often preferred because it can be easily modified despite the number of elements within it.

## Question 9: Give some standard applications of the tree data structure.

i) Analysis of syntax;
ii) Manipulation of mathematical expressions;
iii) Construction of symbol tables.

## Question 20: What are the available methods of storing sequential files?

• Straight and natural merging;
• Polyphase sort;
• Distribution of the first run.

We hope that you find our review of the data structures interview questions helpful in your interview. You may not only stop at this review but also comb through other books to get the most satisfactory knowledge on data structures. Also, make a point to share with us your findings and whether or not you aced your interview with the help of this article. Learning data structures is a good way of complementing your programming career as you get to understand better how things work.