Updated May 6, 2023

## Introduction to Data Structures And Algorithms Interview Questions

Data structures and algorithms interview questions are designed to assess a candidate’s knowledge and proficiency in implementing common data structures and algorithms. In software engineering and computer science, a data structure is a method to store and organize data systematically. At the same time, an algorithm is a step-by-step procedure with instructions to get the desired output.

Preparing for the specific interview questions is crucial to ace a job interview related to data structures and algorithms in 2023. While each interview and job position may vary, grasping the top 15 data structures and algorithms questions and their answers can give you an edge. Doing so will equip you with the necessary knowledge and confidence to succeed in the interview.

To help you prepare, we have compiled a list of the top 2023 Data Structures and algorithms interview questions and answers.

### Part 1 – Data Structures And Algorithms Interview Questions for Freshers

#### 1. What is a data structure?

**Answer:**

A data structure is a way of organizing, storing & retrieving data in a structural & systematic manner. It also defines their relationship with one another through algorithms. A data structure contains a variety of data items to perform various applications. This performance is highly specialized for specific tasks.

#### 2. What are the various data structures available?

**Answer:**

The various data structures available are lists, arrays, stacks, queues, graphs, trees, tables, records, etc. The availability of data structure depends on the programming language.

#### 3. What is an algorithm?

**Answer:**

An algorithm is a step-by-step method to solve a problem. It defines a set of instructions that must be executed to get the desired result. For example, a computer program uses an elaborate algorithm. An algorithm is not the entire code. It is simple logic (solution) to a problem represented using a flowchart or pseudocode.

#### 4. Differentiate file structure from the storage structure.

**Answer:**

File structure deals with secondary or auxiliary memory that remains intact until manually deleted. Storage structure deals with the memory that resides in the main memory of the computer system, i.e., RAM. It is deleted once the function that uses it has completed its execution. The key difference is data storage in the computer system’s memory area.

#### 5. What is a linked list?

**Answer:**

A linked list is a collection of elements linked by pointers or references. Tips help to connect the elements to form a chain. A node is a distinct object of each element. A linked list is a data structure consisting of a group of nodes representing a sequence together.

#### 6. What is the stack?

**Answer:**

A stack is a type of Abstract Data Type (ADT). We use the Stack data structure to store and retrieve values using the Last-In-First-Out (LIFO) algorithm. A stack is a data structure where insertion and deletion occur at a particular time.

#### 7. Why do we use stacks?

**Answer:**

A stack structure dramatically restricts how elements are inserted, retrieved, and removed. Only the most recently inserted element in the stack is retrieved or removed. Stacks follow the LIFO method; adding and retrieving a data item takes only O(n) time. It is used in accessing data in the reverse order in which it arrived. It is frequently used in recursive function calls, expression parsing, depth-first traversal of graphs, etc.

### Part 2 – Data Structures And Algorithms Interview Questions for Experience

#### 8. What are the operations performed on stacks?

**Answer:**

The primary operations performed on a stack are as follows:-

**pop() −**removes the top stack item -Deletion.**peek() −**returns a value of a top item without removing it -Traversal.**isempty() −**checks if the stack is empty –Null check.**isfull() −**checks if the stack is full –No space.

#### 9. What is a queue in the data structure?

**Answer:**

The queue is a linear data structure storing items and opening at both ends. One end serves to enqueue (insert an element), and the other serves to dequeue (remove an element). The First-In-First-Out methodology governs the Queue, meaning that the first data item stored is the first to be made available.

#### 10. What is linear searching?

**Answer:**

Linear search tries to locate an item sequentially. These sequentially arranged data items, arrays, or lists, are accessible in memory locations. Linear search compares expected data items to each item in a list or array. The average case time complexity of the linear search is Ο(n), and the worst-case complexity is Ο(n2). The data in target arrays/lists do not need to be sorted.

#### 11. What is a binary search?

**Answer:**

A binary search applies to already sorted lists or arrays. Binary search, also known as half-interval search, logarithmic search, or binary chop, is a search algorithm that finds the position of a target value within a sorted array. This search selects the middle, dividing the entire list into two sections, and compares the middle part first.

#### 12. What is a graph?

**Answer:**

A graph is a pictorial representation of a collection of objects. A graph is a non-linear data structure consisting of nodes and edges. The points that connect the interconnected objects are vertices, and the links that connect the vertices are edges. A graph data structure contains a finite (potentially mutable) set of vertices, nodes, or points. In an undirected graph, we use a set of unordered pairs of vertices, while in a directed graph, we use a set of ordered pairs.

#### 13. What is a recursive function?

**Answer:**

A recursive function is one that either directly calls itself or calls a function that, in turn, calls itself. Recursive algorithms solve problems by breaking them into simpler sub-problems and solving them iteratively. The output of one operation is the direct input for the next iteration operation.

#### 14. What is the tower of Hanoi?

**Answer:**

The Tower of Hanoi is a mathematical puzzle consisting of three towers (pegs) and multiple rings. All rings are of different sizes and stacked on each other, where the large disk is always beneath the small disk. The aim is to move the tower of a disk from one peg to another without destroying its properties. The main objective is to move the disks one by one from the first to the last peg but cannot stack two discs on top of each other.

#### 15. Give some examples of greedy algorithms?

**Answer:**

The greedy algorithm approach is used to solve the problem listed below:−

- Traveling Salesman issue
- Prim’s Minimal Minimal Spanning Trees
- Kruskal’s Minimal Minimal Spanning Trees
- Dijkstra’s Minimal Spanning Tree Algorithm
- Graph – Map Coloring
- Graph – Vertex Cover
- Knapsack issue
- Job Scheduling Problem

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