# Data Structures Interview Questions

Data structures Interview Questions and Answers, data structures & algorithms, Data structures, and Algorithm Analysis, Data structures, and Program Design.

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### Data Structures Interview Questions and Answers

1. What is Data Structure?

The data structure is a storage that is used to store and organize data. It is a way of arranging data on a computer so that it can be accessed and updated efficiently.

2. What are the common types of Data Structures?

Data structures are being used in almost every program or software system that has been developed. Moreover, data structures come under the fundamentals of Computer Science and Software Engineering.

1. Arrays
An array is a structure of fixed size, which can hold items of the same data type. It can be an array of integers, an array of floating-point numbers, an array of strings or even an array of arrays (such as 2-dimensional arrays). Arrays are indexed, meaning that random access is possible.

A linked list is a sequential structure that consists of a sequence of items in linear order which are linked to each other. Hence, you have to access data sequentially and random access is not possible. Linked lists provide a simple and flexible representation of dynamic sets.

3. Stacks
A stack is a LIFO (Last In First Out — the element placed at last can be accessed at first) structure which can be commonly found in many programming languages.

4. Queues
A queue is a FIFO (First In First Out — the element placed at first can be accessed at first) structure which can be commonly found in many programming languages.

5. Hash Tables
A Hash Table is a data structure that stores values that have keys associated with each of them. Furthermore, it supports lookup efficiently if we know the key associated with the value.

6. Trees
A tree is a hierarchical structure where data is organized hierarchically and are linked together. This structure is different from a linked list whereas, in a linked list, items are linked in a linear order.

7. Heaps
A Heap is a special case of a binary tree where the parent nodes are compared to their children with their values and are arranged accordingly.

8. Graphs
A graph consists of a finite set of vertices or nodes and a set of edges connecting these vertices.

3. What are some applications of Data Structures?

• Numerical analysis
• Operating system
• Artificial Inteligence
• Compiler design
• Database management,
• Graphics,
• Statistical analysis,
• and Simulation.

4. What is the difference between file structure and storage structure?

The difference lies in the memory area accessed. Storage structure refers to the data structure in the memory of the computer system, whereas file structure represents the storage structure in the auxiliary memory.

5. What is an Array?

An array is a collection of similar data elements stored at contiguous memory locations. It is the simplest data structure where each data element can be accessed directly by only using its index number.

6. What is a Queue?

A queue is a data structure that can simulate a list or stream of data. In this structure, new elements are inserted at one end, and existing elements are removed from the other end.

7. What is a Stack?

A stack is a data structure in which only the top element can be accessed. As data is stored in the stack, each data is pushed downward, leaving the most recently added data on top.

8. Linked lists of linear or non-linear type?

A linked list is considered both linear and non-linear data structure depending upon the situation.

On the basis of data storage, it is considered as a non-linear data structure.

On the basis of the access strategy, it is considered as a linear data structure.

9. When is a binary search best applied?

Binary search is a type of algorithm. It is best applied to search in a list in which the elements are already in order or sorted.

10. When an Ordered list is used?

When programming a website using HTML (Hypertext Markup Language) coding, an ordered list is used to create a list of items that are numbered to show the order they should go in.

11. How do you insert a new item in a binary search tree?

Insert function is used to add a new element in a binary search tree at the appropriate location. Insert function is to be designed in such a way that, it must node violate the property of binary search tree at each value.

12. What are push and pop operations in Data Structures?

The push operation is done to insert a component into the stack. The new component is added at the topmost position of the stack.

The pop operation is done to delete the topmost component from the stack. But, before deleting the value, we need to first check if TOP=NULL because if this is the situation, then it indicates the stack is empty and no more further deletions can be done.

13. Differentiate NULL and VOID?

Null is a value, whereas Void is a data type identifier. A variable that is given a Null value indicates an empty value. The void is used to identify pointers as having no initial size.

14. What is the use of dynamic Data Structures?

Dynamic data structures are flexible and size changes can occur during insertion or deletion operations. Dynamic data structures play a key role in programming because they provide the programmer with the flexibility to adjust the memory consumption of programs.

15. What are the types of searching used in Data Structures?

• Linear Search.
• Binary Search.
• Jump Search.
• Interpolation Search.
• Exponential Search.

16. What is FIFO?

FIFO stands for First-in, First-out, and is used to represent how data is accessed in a queue. Data has been inserted into the queue list the longest is the one that is removed first.

17. What is Algorithm?

The algorithm is a step-by-step procedure, which defines a set of instructions to be executed in certain order to get the desired output.

18. What is linear data structure?

A linear data structure has sequentially arranged data items. The next time can be located in the next memory address. It is stored and accessed in a sequential manner. Array and list are example of linear data structure.

19. What are common operations that can be performed on a data structure?

The following operations are commonly performed on any data structure −

• Insertion − adding a data item
• Deletion − removing a data item
• Traversal − accessing and/or printing all data items
• Searching − finding a particular data item
• Sorting − arranging data items in a pre-defined sequence

20. Briefly explain the approaches to develop algorithms.

There are three commonly used approaches to develop algorithms −

Greedy Approach − finding a solution by choosing the next best option

Divide and Conquer − diving the problem to a minimum possible sub-problem and solving them independently

Dynamic Programming − diving the problem to a minimum possible sub-problem and solving them combinedly

21. What Data Abstraction?

Data abstraction helps in dividing complex data problems into smaller, easy-to-manage parts. It starts with specifying all the involved data objects and the various operations to be performed on the same without stressing too much about the way data is stored.

Python Data Structures

Python Tutorial for Beginners