**Data Structure Interview Questions:** Data structures are fundamental building blocks of computer science and programming. They enable us to store, organize and manipulate data efficiently and effectively. As a result, data structures are a key topic in software development interviews, as they test a candidate’s knowledge and understanding of fundamental concepts.

This article will explore some of the most commonly asked data structure interview questions and their solutions. We will cover topics such as arrays, linked lists, stacks, queues, trees, and graphs and discuss their applications and implementations. This article aims to help aspiring software developers and programmers prepare for their data structure interviews and better understand these fundamental concepts.

## Data Structure Interview Questions

**What is the data structure?**** Ans:** A data structure is a way of organising data that considers not only the items stored but also their relationship to each other. Advanced knowledge about the relationship between data items allows the designing of efficient algorithms for manipulating data.

Application of data structures.

- Compiler Design
- Operating System
- Database Management System
- Statistical analysis package
- Numerical Analysis
- Graphics
- Artificial Intelligence
- Simulation

**What are the major data structures used in the following areas :****Ans:**

- RDBMS, Network data model, and Hierarchical data model.
- RDBMS = Array (i.e. Array of structures)
- Network data model = Graph
- Hierarchical data model = Trees

**If you are using C language to implement the heterogeneous linked list, what pointer type will you use?****Ans:** The heterogeneous linked list contains different data types in its nodes, and we need a link, pointer to connect them. It is not possible to use ordinary pointers for this. So we go for a void pointer. A void pointer is capable of storing the pointer to any type as it is a generic pointer type.

**A minimum number of queues needed to implement the priority queue?****Ans:** Two. One queue is used for the actual storing of data and another for storing priorities.

**What are the data structures used to perform recursion?****Ans:**– Stack. Because of its LIFO (Last In First Out) property files? It remembers its ‘caller’ so knows whom to return when the function has to return. Recursion makes use of system stack for storing the return addresses of the function calls. Every recursive function has its equivalent iterative (non-recursive) function. Even when such equivalent iterative procedures are written, explicit stack is to be used.

**What are the notations used in the Evaluation of Arithmetic Expressions using the prefix and postfix forms?****Ans:** Polish and Reverse Polish notations.

Convert the expression ((A + B) * C – (D – E) ^ (F + G)) to equivalent Prefix and Postfix notations.

Prefix Notation: – * +ABC ^ – DE + FG

Postfix Notation: AB + C * DE – FG + ^ –

**Sorting is not possible by using which of the following methods? (Insertion, Selection, Exchange, Deletion)****Ans:** Sorting is not possible in Deletion. Using insertion, we can perform insertion sort, using selection we can perform selection sort, using exchange we can perform the bubble sort (and other similar sorting methods). But no sorting method can be done just using deletion.

**What are the methods available in storing sequential files?****Ans:** Straight merging, Natural merging, Polyphase sort, Distribution of Initial runs.

**List out a few of the Application of tree data-structure?|****Ans:** The manipulation of Arithmetic expression, Symbol Table construction, Syntax analysis.

**In tree construction which is the suitable, efficient data structure? (Array, Linked list, Stack, Queue)****Ans:** the Linked list is the suitable, efficient data structure.

**What is the type of algorithm used in solving the 8 Queens problem?**

**Ans:**Backtracking.

**In an AVL tree, at what condition the balancing is to be done?**

**Ans:**If the ‘pivotal value’ (or the ‘Height factor’) is greater than 1 or less than -1.

**What is the bucket size, when the overlapping and collision occur at the same time?****Ans:**– One. If there is only one entry possible in the bucket, when the collision occurs, there is no way to accommodate the colliding value. This results in the overlapping of values.

**In RDBMS, what is the efficient data structure used in the internal storage representation?****Ans:**– B+ tree. Because in B+ tree, all the data is stored only in leaf nodes, that makes searching easier. This corresponds to the records that shall be stored in leaf nodes.

**What is a spanning Tree?****Ans:** A spanning tree is a tree associated with a network. All the nodes of the graph appear on the tree once. A minimum spanning tree is a spanning tree organised so that the total edge weight between nodes is minimised.

**Does the minimum spanning the tree of a graph give the shortest distance between any 2 specified nodes?****Ans:**– No. The Minimal spanning tree assures that the total weight of the tree is kept at its minimum. But it doesn’t mean that the distance between any two nodes involved in the minimum spanning tree is minimum.

**Which is the simplest file structure? (Sequential, Indexed, Random)****Ans:**– Sequential is the simplest file structure.

**Whether Linked List is linear or Non-linear data structure?****Ans:**– According to Access strategies, the Linked list is a linear one. and according to Storage Linked List is a Non-linear one.

**What is the difference between the HEAP and the STACK?****Ans:**– HEAP is used to store dynamically allocated memory (malloc). STACK stores static data (int, const).

**Where in memory are HEAP and the STACK located relative to the executing program?****Ans:**– The STACK and HEAP are stored “below” the executing program. The HEAP “grows” toward the program executable while the STACK grows away from it.

**Describe the data structures of a double-linked list.****Ans:** -A double-linked list structure contains one pointer to the previous record in the list and a pointer to the next record in the list plus the record data.

**How do you insert a record between two nodes in a doubly-linked list?****Ans:**– Previous R; Data R; Next R; To insert a record (B) between two others (A and C): Previous.B = A; Next.B = C; Next.A = B; Previous.C = B;

**In which data structure, elements can be added or removed at either end, but not in the middle?****Ans:**– queue

**Which one is faster? A binary search of an ordered set of elements in an array or a sequential search of the elements.****Ans:**– binary search

**What is a balanced tree?****Ans:**– A binary tree is balanced if the depth of two subtrees of every node never differ by more than one

**Which data structure is needed to convert infix notations to a notation?****Ans:**– stack

**What is the data structure, or how would you define data structure?****Ans:**– In programming, the term data structure refers to a scheme for organising a related piece of information. Data Structure = Organized Data + Allowed Operations

**Which data structures we can implement using link list?****Ans:** queue and stack

**List different types of data structures?****Ans:** Different type of data structure are; Link list, queue, stack, trees, files, graphs.

**Conclusion:**

These interview questions related to Data Structures and Algorithms (DSA) will provide you with an idea of the types of questions that may be asked during an interview. While you may anticipate many of these questions, it is also necessary to dedicate time to your learning process. It is equally essential to have a solid grasp of fundamental data structures, how to access elements from arrays or linked lists, and coding for data science.