Top 50 Data Structures Interview Questions & Answers (2022)

1) What is data structure?
Data structure refers to the way data is organized and manipulated. It seeks to find ways to make data entree more effective. When dealing with the data structure, we not entirely focus on one piece of data but the different stage set of data and how they can relate to one another in an organized manner.

2) Differentiate between file and structure storage structure.
The key difference between both the datum structure is the memory area that is being accessed. When dealing with the structure that resides the independent memory of the computer system, this is referred to as storage structure. When dealing with an aide structure, we refer to it as file structures .
3) When is a binary search best applied?
A binary search is an algorithm that is best applied to search a list when the elements are already in order or sorted. The list is searched starting in the middle, such that if that middle value is not the prey search key, it will check to see if it will continue the search on the lower half of the tilt or the higher half. The schism and search will then continue in the lapp manner .
4) What is a linked list?
A linked number is a sequence of nodes in which each lymph node is connected to the node following it. This forms a chain-like link for data storage .
5) How do you reference all the elements in a one-dimension array?
To reference all the elements in a one -dimension array, you need to use an index loop, So that, the counter runs from 0 to the range size minus one. In this manner, You can reference all the elements in succession by using the loop buffet as the array subscript .
6) In what areas do data structures are applied?
Data structures are all-important in about every expression where datum is involved. In general, algorithms that involve efficient data structure is applied in the follow areas : numerical analysis, operating system, A.I., compiler purpose, database management, graphics, and statistical analysis, to name a few .
7) What is LIFO?
LIFO is a short shape of last In First Out. It refers how data is accessed, stored and retrieved. Using this outline, data that was stored concluding should be the one to be extracted first. This besides means that in orderliness to gain access to the first gear data, all the other data that was stored before this first data must first be retrieved and extracted .
8 ) What is a queue?
A queue is a data social organization that can simulate a number or stream of data. In this structure, new elements are inserted at one goal, and existing elements are removed from the other end .
9) What are binary trees?
A binary tree is one character of data structure that has two nodes, a leave node, and a right node. In program, binary trees are an reference of the linked tilt structures .
10) Which data structures are applied when dealing with a recursive function?
recursion, is a serve that calls itself based on a end discipline, makes use of the push-down list. Using LIFO, a call to a recursive officiate saves the return address so that it knows how to return to the calling function after the birdcall terminates .
11) What is a stack?
A stack is a data social organization in which only the top element can be accessed. As data is stored in the stack, each data is pushed down, leaving the most recently added data on crown .
12) Explain Binary Search Tree
A binary search tree stores data in such a way that they can be retrieved very efficiently. The leave subtree contains nodes whose keys are less than the node ’ south key value, while the right subtree contains nodes whose keys are greater than or equal to the node ’ sulfur key value. furthermore, both subtrees are besides binary search trees .
13) What are multidimensional arrays?
Multidimensional arrays make consumption of multiple indexes to store data. It is utilitarian when storing data that can not be represented using single dimensional index, such as data representation in a board game, tables with data stored in more than one column .
14) Are linked lists considered linear or non-linear data structures?
It depends on where you intend to apply yoke lists. If you based it on repositing, a linked list is considered non-linear. On the early hand, if you based it on access strategies, then a linked list is considered analogue .
15) How does dynamic memory allocation help in managing data?
apart from being able to store simple structured data types, dynamic memory allotment can combine individually allocated structure blocks to form complex structures that expand and condense as needed .
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 an ordered list?
An order list is a list in which each node ’ south position in the list is determined by the measure of its key part, so that the key values form an increasing sequence, as the list is traversed .
18) What is merge sort?
Merge screen, is a divide-and-conquer approach for sorting the datum. In a sequence of data, adjacent ones are merged and sorted to create bigger sorted lists. These sorted lists are then merged again to form an even bigger classify list, which continues until you have one single sorted list .
19) Differentiate NULL and VOID
Null is a rate, whereas Void is a datum type identifier. A varying that is given a Null respect indicates an empty value. The invalidate is used to identify pointers as having no initial size .
20) What is the primary advantage of a linked list?
A linked list is an ideal datum structure because it can be modified easily. This means that editing a linked list works careless of how many elements are in the number .
21) What is the difference between a PUSH and a POP?
Pushing and popping applies to the way data is stored and retrieved in a push-down list. A push denotes data being added to it, meaning data is being “ pushed ” into the push-down list. On the other hand, a pop denotes data retrieval, and in particular, refers to the topmost data being accessed .
22) What is a linear search?
A linear search refers to the room a target key is being searched in a consecutive data structure. In this method acting, each element in the list is checked and compared against the target key. The process is repeated until found or if the end of the file has been reached .
23) How does variable declaration affect memory allocation?
The measure of memory to be allocated or reserved would depend on the data type of the variable being declared. For example, if a variable is declared to be of integer character, then 32 bits of memory memory will be reserved for that variable .
24) What is the advantage of the heap over a stack?
The stack is more compromising than the stack. That ’ s because memory space for the heap can be dynamically allocated and de-allocated as needed. however, the memory of the pile can at times be slower when compared to that smokestack .
25) What is a postfix expression?
A suffix expression is an expression in which each operator follows its operands. The advantage of this imprint is that there is no want to group sub-expressions in parentheses or to consider operator precedence.

26) What is Data abstraction?
Data abstraction is a potent joyride for breaking down complex datum problems into accomplishable chunks. This is applied by initially specifying the data objects involved and the operations to be performed on these data objects without being excessively concerned with how the datum objects will be represented and stored in memory .
27) How do you insert a new item in a binary search tree?
Assuming that the data to be inserted is a singular measure ( that is, not an existing entrance in the tree ), check beginning if the corner is empty. If it ’ s empty, just insert the new detail in the root lymph node. If it ’ s not empty, refer to the newfangled token ’ sulfur key. If it ’ mho smaller than the root ’ second key, insert it into the root ’ mho left subtree, otherwise, insert it into the root ’ second right subtree .
28) How does a selection sort work for an array?
The choice screen is a fairly intuitive sorting algorithm, though not inevitably efficient. In this process, the smallest chemical element is inaugural located and switched with the element at subscript zero, thereby placing the smallest component in the first put .
The smallest element remaining in the subarray is then located next to subscripts 1 through n-1 and switched with the element at subscript 1, thereby placing the second smallest element in the second position. The steps are repeated in the same manner till the survive element .
29) How do signed and unsigned numbers affect memory?
In the case of sign numbers, the first bite is used to indicate whether positive or negative, which leaves you with one bit short. With unsigned numbers, you have all bits available for that count. The effect is best seen in the number range ( an unsigned 8-bit number has a range 0-255, while the 8-bit gestural act has a range -128 to +127 .
30) What is the minimum number of nodes that a binary tree can have?
A binary tree can have a minimum of zero nodes, which occurs when the nodes have NULL values. furthermore, a binary tree can besides have 1 or 2 nodes .
31) What are dynamic data structures?
Dynamic data structures are structures that expand and compress as a plan runs. It provides a compromising mean of manipulating data because it can adjust according to the size of the data .
32) In what data structures are pointers applied?
Pointers that are used in connect list have diverse applications in the datum structure. Data structures that make consumption of this concept include the Stack, Queue, Linked List and Binary Tree .
33) Do all declaration statements result in a fixed reservation in memory?
Most declarations do, with the exemption of pointers. Pointer declaration does not allocate memory for data, but for the address of the pointer variable. actual memory allotment for the datum comes during run-time .
34) What are ARRAYs?
When dealing with arrays, data is stored and retrieved using an index that refers to the element number in the datum sequence. This means that data can be accessed in any order. In programming, an array is declared as a variable having a number of index elements .
35) What is the minimum number of queues needed when implementing a priority queue?
The minimal number of queues needed in this casing is two. One line up is intended for sorting priorities while the other queue is used for actual storage of data .
36) Which sorting algorithm is considered the fastest?
There are many types of sorting algorithm : immediate sort, bubble sort, balloon sort, base sort, unify sort, etc. not one can be considered the fastest because each algorithm is designed for a particular datum structure and data fixed. It would depend on the datum stage set that you would want to sort .
37) Differentiate STACK from ARRAY.
batch follows a LIFO convention. It means that data access follows a sequence wherein the last datum to be stored when the first one to be extracted. Arrays, on the other hired hand, does not follow a particular holy order and rather can be accessed by referring to the index chemical element within the align .
38) Give a basic algorithm for searching a binary search tree.

  1. if the tree is empty, then the target is not in the tree, end search
    2. if the tree is not empty, the target is in the tree
    3. check if the target is in the root item
    4. if a target is not in the root item, check if a target is smaller than the root’s value
    5. if a target is smaller than the root’s value, search the left subtree
    6. else, search the right subtree

39) What is a dequeue?
A dequeue is a double-ended queue. This is a social organization wherein elements can be inserted or removed from either conclusion .
40) What is a bubble sort and how do you perform it?
A bubble screen is one sort technique that can be applied to data structures such as an range. It works by comparing adjacent elements and exchanges their values if they are out of order. This method lets the smaller values “ bubble ” to the top of the tilt, while the larger respect sinks to the bottomland .
41) What are the parts of a linked list?
A linked tilt typically has two parts : the fountainhead and the tail. Between the lead and tail lie the actual nodes. All these nodes are linked consecutive .
42) How does selection sort work?
Selection sort works by picking the smallest number from the list and placing it at the front. This process is repeated for the moment position towards the end of the tilt. It is the simplest sort algorithm .
43) What is a graph?
A graph is one type of data social organization that contains a set of order pairs. These ordered pairs are besides referred to as edges or arch and are used to connect nodes where data can be stored and retrieved .
44) Differentiate linear from a nonlinear data structure.
The linear data social organization is a structure wherein data elements are adjacent to each early. Examples of analogue data structure include arrays, linked lists, stacks, and queues. On the other hired hand, a non-linear data structure is a structure wherein each data chemical element can connect to more than two adjacent data elements. Examples of nonlinear data structure include trees and graph .
45) What is an AVL tree?
An AVL tree is a type of binary search corner that is constantly in a state of partially balanced. The remainder is measured as a deviation between the heights of the subtrees from the ancestor. This self-balancing corner was known to be the first datum structure to be designed as such .
46) What are doubly linked lists?
doubly linked lists are a extra type of linked list wherein traversal across the datum elements can be done in both directions. This is made possible by having two links in every node, one that links to the next node and another one that connects to the previous node .
47) What is Huffman’s algorithm?
Huffman ’ mho algorithm is used for creating extended binary trees that have minimum slant path lengths from the given weights. It makes habit of a table that contains the frequency of happening for each data chemical element .
48) What is Fibonacci search?
Fibonacci search is a search algorithm that applies to a classify array. It makes habit of a divide-and-conquer approach path that can importantly reduce the clock needed in order to reach the prey element .
49) Briefly explain recursive algorithm.
recursive algorithm targets a problem by dividing it into smaller, manageable sub-problems. The end product of one recursion after processing one sub-problem becomes the input to the next recursive process .
50) How do you search for a target key in a linked list?

To find the target key in a connect tilt, you have to apply consecutive search. Each node is traversed and compared with the target key, and if it is different, then it follows the connection to the future lymph node. This traversal continues until either the target key is found or if the final node is reached .

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