Top 50 Data Structure Interview Questions and Answers 2022 for Preparation

The data structure is a practice that determines how to manage and manipulate the data. It also describes the connection between them. Some Data Structures examples are arrays, Stack, Linked List, Queue, etc. Data Structures are the core part of many computer science algorithms as they allow the developers to manage the data efficiently.

2. Explain types of Data Structures?

Linear Data Structure: If all the elements are positioned in sequential order then it makes a linear data structure. The elements are held in a non-hierarchical manner where every item has successors and predecessors but the first and last elements. Non-Linear Data Structure: The Non-linear data structure does not create a sequence i.e. every item or element is linked with two or more different items in a non-linear sequence. The data elements are not positioned in a sequential structure.

3. Tell the area of applications in which Data Structure is used.

Following are the areas of computer science in which Data Structure is used: Compiler Design, Database Management System, Operating System, Graphics, Statistical analysis package, Artificial Intelligence, Numerical Analysis, Simulation

4. Differentiate between storage structure and file structure?

The primary difference between storage structure and file structure is on the basis of the memory area that is being utilized. Storage structure: It shows the data structure in the computer memory. File structure: It shows the storage structure in the auxiliary memory.

RDBMS uses an Array data structure The network data model uses Graph The hierarchal data model uses Trees

6. To perform recursion, which data structure is used?

To perform recursion, the stack data structure is used because of its last in first out nature. The operating system supports the stack to save the iteration variables at individual function calls.

7. Explain a Stack?

It is an ordered list in which insertion and deletion can be executed only at one end known as the top. It is a recursive data format having a pointer at its top element. The stack is also known as Last-In-First-Out (LIFO) list i.e. the element that is inserted first in the stack will be eliminated last from the stack.

8. Name the area of applications of the stack data structure?

Backtracking Expression evaluation Function calling and return Memory Management

9. Name the operations that can be executed on a stack?

Push Operations Peek Operations Pop Operations

10. Mention the stack overflow condition.

Overflow occurs when top = Maxsize -1

11. Differentiate between PUSH and POP?

These operations determine how data is reserved and retrieved in a stack. PUSH: PUSH determines that data is “inserted” into the stack. POP: POP determines data retrieval, which means data is deleted from the stack.

12. Tell the steps applied in the insertion and deletion of an element in the stack.

Push: Increase the variable top so that it can guide to the next memory allocation Duplicate the item to the array index value equivalent to the top Repeat steps 1 and 2 until the stack overflows Pop: Reserve the topmost element into another variable Decrease the value of the top Return the topmost element

13. Explain postfix expression?

An expression in which operatives follow the operands is called postfix expression. The primary advantage of this expression is that there is no requirement to group sub-expressions in parentheses and also no need to consider operator precedence. The expression “a + b” will be shown as “ab+” in postfix notation.

14. Write postfix form of the given expression: (A + B) * (C - D)

AB+CD-*

15. Name the notations used in the Evaluation of Arithmetic Expressions using prefix and postfix forms?

Polish and Reverse Polish notations is used in the Evaluation of Arithmetic Expressions using prefix and postfix forms

16. Explain an array?

They are described as the cluster of the same type of data items stored at contiguous memory locations. It is one of the simplest data structures in which every data element can be erratically accessed by using its index number.

17. How to position all the elements in a 1-D array?

By using an indexed loop which counters runs from 0 to the array size -1. In this way, you can position all the elements in line by operating the loop counter as the array subscript.

18. Explain a multidimensional array?

The multidimensional array can be described as the array of arrays in which, the data is reserved in a tabular structure that includes rows and columns. 2D arrays are made to enforce a relational database similar to the data structure. It gives ease of carrying the bulk of data at one time that can be handed to any number of functions wherever needed.

19. Tell the way the elements of a two-dimensional array are reserved in the memory?

Two techniques are used through which the elements of a two-dimensional array can be reserved in the memory. Row-Major Order: In row-major ordering, all the rows of the two-dimensional array are reserved into the memory closely. Preferably, the 1st row of the array is reserved in the memory thoroughly, and then the 2nd row of the array is reserved in the memory thoroughly, and so on till the last row. Column-Major Order: In column-major ordering, all the columns of the 2D array are reserved into the memory closely. Preferably, the 1st column of the array is reserved into the memory thoroughly, and then the 2nd row of the array is reserved into the memory thoroughly, and so on till the last column of the array.

20. Compute the address of a spontaneous element present in a two-dimensional array, when the given base address is BA.

Row-Major Order: If the array is called as a[m][n] where m represent the number of rows whereas n represents the number of columns, then the address of an element a[i][j] of the array reserved in row-major order is calculated as, Address(a[i][j]) = B. A. + (i * n + j) * size Column-Major Order: If an array is called as a[m][n] where m represent the number of rows whereas n represents the number of columns, then the address of an element a[i][j] of the array reserved in column-major order is calculated as Address(a[i][j]) = ((j*m)+i)*Size + BA.

21. Explain Linked List Data structure.

A linked list is the group of randomly reserved data objects known as nodes. In this linked list, each node is connected to its adjacent node via pointer. A node includes two fields that are Data Field and Link Field.

22. How are linked list evaluated linear or non-linear data structures?

A linked list is evaluated linear and non-linear data structure on the basis of these situations. Based on data storage, it is evaluated as a non-linear data structure. Based on the access strategy, it is evaluated as a linear data structure.

23. Tell the benefits of Binary search over linear search?

There is a moderately small number of comparisons in binary search than in linear search. In an average case, the linear search carries O(n) time to search a list of n elements whereas Binary search carries O(log n) time to search a list of n elements.

24. Write a code in C to make a node in the singly linked list.

struct node
{
int data;
struct node *next;
};
struct node *head, *ptr;
ptr = (struct node *)malloc(sizeof(struct node));

25. What pointer type should you use in C language to implement the heterogeneous linked list?

The heterogeneous linked list includes various data types so it is impossible to use common pointers. For this, we use a generic pointer type for example a void pointer as it is capable of keeping a pointer to any type.

26. Explain the doubly-linked list?

The doubly linked list is a complex type of linked list in which a node includes a pointer to the prior and the next node in the series. Anode include three parts: node data pointer to the next node in series (next pointer) pointer to the previous node (previous pointer).

27. Write a C program to insert a node in circular singly list at the beginning.

#include<stdio.h>
#include<stdlib.h>
void beg_insert(int);
struct node
{
int data;
struct node *next;
};
struct node *head;
void main ()
{
int choice,item;
do
{
printf("\nEnter the item which you want to insert?\n”);
scanf("%d”,&item);
beg_insert(item);
printf("\nPress 0 to insert more ?\n”);
scanf("%d”,&choice);
}while(choice == 0);
}
void beg_insert(int item)
{

struct node *ptr = (struct node *)malloc(sizeof(struct node));    
struct node *temp;  
if(ptr == NULL)    
{    
    printf("\nOVERFLOW");    
}    
else     
{    
    ptr -> data = item;    
    if(head == NULL)    
    {    
        head = ptr;    
        ptr -> next = head;    
    }    
    else     
    {       
        temp = head;    
        while(temp->next != head)    
            temp = temp->next;    
        ptr->next = head;     
        temp -> next = ptr;     
        head = ptr;    
    }     
printf("\nNode Inserted\n");  
}

}

28. Explain the queue data structure.

A queue can be described as an ordered list that permits insert operations to be run at one end called REAR and delete operations to be run at the other end called FRONT.

29. Name some applications of queue data structure.

It is used in the asynchronous transfer of data such as pipes, file IO, sockets. It is used as waiting list for one shared resource like a printer, CPU. It is used to keep the playlist in media players to add and remove the tunes from the playlist. It is used as buffers in applications like MP3 media players, CD players, etc. It is used in operating systems for managing interrupts.

30. What are the disadvantages of array implementation of Queue?

Memory Wastage: The array space that is used to reserve queue elements, cannot be reutilized to reserve the elements of that queue as the elements can only be inserted at the front end and the value of the front end might be so high so, all the space before that, it cannot be filled. Array Size: There are some situations when we need to extend the queue to insert more elements if we use an array to execute a queue, It will nearly impossible to extend the array size, thus choosing the correct array size is still a problem in array execution of a queue.

31. Tell the benefits of Selection Sort?

Easy and simple to implement. Selection Sort is used for small data sets. It is 60% more efficient than bubble sort.

32. Explain a dequeue?

Dequeue (also called double-ended queue) can be described as an ordered set of elements in which at both the ends, i.e. front and rear the insertion and deletion can be run.

33. Tell the minimum number of queues that are required to implement a priority queue?

Two queues are required to implement a priority queue. One queue is used to reserve the data elements, and the other queue is used for storing priorities.

34. Explain the tree data structure.

The Tree is a recursive data format including the set of one or more data nodes where one node is defined as the root of the tree while the other nodes are known as the children of the root. The nodes other than the root node are divided into nonempty sets where each one of them is to be known as a sub-tree.

35. Name the types of trees in the Data Structure.

General Tree Expression Tree Binary Tree Forests Tournament Tree Binary Search Tree

36. Explain Binary trees?

A binary tree is a unique type of generic tree. In this tree, each node can have a maximum of two children. A binary tree is commonly partitioned into 3 disjoint subsets, i.e. the root of the node, left binary sub-tree, and Right binary sub-tree.

37. Make a C code to work in-order traversal on a binary tree.

void in-order(struct treenode *tree)
{
if(tree != NULL)
{
in-order(tree→ left);
printf("%d”,tree→ root);
in-order(tree→ right);
}
}

38. Tell us the maximum number of nodes required in a binary tree of height k?

2k+1-1 where k >= 1

39. Name the data structure suits the most in the tree construction?

Queue data structure suits the most in the tree construction.

40. Differentiate between NULL and VOID?

Null is a value type and Void is a data type identifier. A null variable shows an empty value and a void is used to determine pointers as they don’t have an initial size.

41. Write the recursive C function code to know the number of nodes available in a binary tree.

int count (struct node* t)
{
if(t)
{
int l, r;
l = count(t->left);
r=count(t->right);
return (1+l+r);
}
else
{
return 0;
}
}

42. Write a code of recursive C function to compute the height of a binary tree.

int countHeight(struct node* t)
{
int l,r;
if(!t)
return 0;
if((!(t->left)) && (!(t->right)))
return 0;
l=countHeight(t->left);
r=countHeight(t->right);
return (1+((l>r)?l:r));
}

43. Is AVL Tree be more useful in all the operations than the Binary search tree?

AVL tree regulates the height of the binary search tree by not allowing it to be skewed. The time carried for all operations in a binary search tree of height h is denoted as O(h). Yet, it can be expanded to O(n) if the BST evolves to skewed (in the worst case). By restricting this height to log n, the AVL tree assesses an upper bound on each operation to be O(log n).

44. Tell some properties of B Tree?

Every node in a B-Tree mostly includes m children. Every node in a B-Tree excluding the root node and the leaf node that includes at least m/2 children. All leaf nodes must be at the same level. The root nodes must have at least 2 nodes.

45. Name Some Applications of Multi-linked Structures?

Index generation. Sparse matrix

46. Name some applications of Tree-data structure?

Symbol Table construction The manipulation of Arithmetic expression, Hierarchal data model Syntax analysis

47. Explain the graph data structure?

A graph G can be described as an ordered set G(V, E) where V(G) defines the set of vertices and E(G) defines the set of edges that are connecting these vertices. A graph creates a cyclic tree, where the vertices (Nodes) sustain complex relationships among them rather than having parent-child relations.

48. Explain cycle, path, and circuit?

Path: A Path is the series of adjacent vertices linked by the edges with no limitations. Cycle: A Cycle can be described as the closed path where the initial vertex is similar to the end vertex. Any vertex can’t be visited twice in the path. Circuit: A Circuit can be described as the closed path where the initial vertex is similar to the end vertex. Any vertex can be repeated.

49. Name the data structures used in graph implementation.

The adjacency matrix is used in the sequential representation. The adjacency list is used in Linked representation.

50. Name the data structures used in DFS and BFS algorithms?

The stack data structure is used in the DFS algorithm. The queue data structure is used in the BFS algorithm

Top 50 Data Structure Interview Questions and Answers 2022 for Preparation

Data Structure Interview Questions

Data Structure Interview Questions and Answers

Recent Articles

Top 40 Jenkins Interview Questions And Answers For Freshers/Experienced

Prepare From Top Linux Interview Questions And Answers