# Data Structure Interview Questions

Individuals who are going to attend the Data Structure Interview round can make their preparation better with the help of Top 30 Data Structure Interview Questions & Answers.

On this web page, you will get the most important questions which are generally asked in the Data Structure Interview round. Usually these types of questions are asked to both freshers as well as experienced candidates.

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## Data Structure Interview Questions

Top 30 Data Structure Interview Questions & Answers

Some most important Data Structure Interview questions and answers for freshers/ experienced aspirants are mentioned below for the convenience of contenders.

Question-1: What is a Data Structure?

Answer: A data structure is a way of organizing the data so that the data can be used efficiently. Different kinds of data structures are suited to different kinds of applications, and some are highly specialized to specific tasks.

Question-2: What are linear and non linear data Structures?

Answer: Linear: A data structure is said to be linear if its elements form a sequence or a linear list. Examples: Array. Linked List, Stacks and Queues

Non-Linear: A data structure is said to be non-linear if traversal of nodes is nonlinear in nature. Example: Graph and Trees.

Question-3: What is a linked list?

Answer: A linked list is a sequence of nodes in which each node is connected to the node following it. This forms a chain-like link of data storage.

Question-4: What is a stack?

Answer: 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.

Question-5: Which data structures is applied when dealing with a recursive function?

Answer: Recursion, which is basically a function that calls itself based on a terminating condition, makes use of the stack. Using LIFO, a call to a recursive function saves the return address so that it knows how to return to the calling function after the call terminates.

Question-6: Explain Binary Search Tree?

Answer: A binary search tree stores data in such a way that they can be retrieved very efficiently. The left sub-tree contains nodes whose keys are less than the node’s key value, while the right sub-tree contains nodes whose keys are greater than or equal to the node’s key value. Moreover, both sub-trees are also binary search trees.

Question-7: What is LIFO?

Answer: LIFO is short for Last In First Out, and refers to how data is accessed, stored and retrieved. Using this scheme, data that was stored last, should be the one to be extracted first. This also means that in order to gain access to the first data, all the other data that was stored before this first data must first be retrieved and extracted.

Question-8: What is a queue?

Answer: A queue is a data structures that can simulates 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.

Question-9: What are multidimensional arrays?

Answer: Multidimensional arrays make use of multiple indexes to store data. It is useful when storing data that cannot be represented using a single dimensional indexing, such as data representation in a board game, tables with data stored in more than one column.

Question-10: Are linked lists considered linear or non-linear data structures?

Answer: It actually depends on where you intend to apply linked lists. If you based it on storage, a linked list is considered non-linear. On the other hand, if you based it on access strategies, then a linked list is considered linear.

Question-11: What is FIFO?

Answer: FIFO is short 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.

Question-12: What is an ordered list?

Answer: An ordered list is a list in which each node’s position in the list is determined by the value of its key component, so that the key values form an increasing sequence, as the list is traversed.

Question-13: What is merge sort?

Answer: Merge sort takes a divide-and-conquer approach to sorting data. 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 sorted list, which continuous until you have one single sorted list.

Question-14: Differentiate NULL and VOID.

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

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Answer: A linked list is a very ideal data structure because it can be modified easily. This means that modifying a linked list works regardless of how many elements are in the list.

Question-16: What is a linear search?

Answer: A linear search refers to the way a target key is being searched in a sequential data structure. Using this method, each element in the list is checked and compared against the target key, and is repeated until found or if the end of the list has been reached.

Question-17: What is the difference between a PUSH and a POP?

Answer: Pushing and popping applies to the way data is stored and retrieved in a stack. A push denotes data being added to it, meaning data is being “pushed” into the stack. On the other hand, a pop denotes data retrieval, and in particular refers to the topmost data being accessed.

Question-18: How does variable declaration affect memory allocation?

Answer: The amount 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 type, then 32 bits of memory storage will be reserved for that variable.

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Question-19: What is a postfix expression?

Answer: A postfix expression is an expression in which each operator follows its operands. The advantage of this form is that there is no need to group sub-expressions in parentheses or to consider operator precedence.

Question-20: What is the minimum number of nodes that a binary tree can have?

Answer: A binary tree can have a minimum of zero nodes, which occurs when the nodes have NULL values. Furthermore, a binary tree can also have 1 or 2 nodes.

Question-21: What are dynamic data structures?

Answer: Dynamic data structures are structures that expand and contract as a program runs. It provides a flexible means of manipulating data because it can adjust according to the size of the data.

Question-22: In what data structures are pointers applied?

Answer: Pointers that are used in linked list have various applications in data structure. Data structures that make use of this concept include the Stack, Queue, Linked List and Binary Tree.

Question-23: What are ARRAYs?

Answer: When dealing with arrays, data is stored and retrieved using an index that actually refers to the element number in the data sequence. This means that data can be accessed in any order. In programming, an array is declared as a variable having a number of indexed elements.

Question-24: Differentiate STACK from ARRAY.

Answer: Data that is stored in a stack follows a LIFO pattern. This means that data access follows a sequence wherein the last data to be stored will the first one to be extracted. Arrays, on the other hand, does not follow a particular order and instead can be accessed by referring to the indexed element within the array.

Question-25: What is a dequeue?

Answer: A dequeue is a double-ended queue. This is a structure wherein elements can be inserted or removed from either end.

Question-26: What is a bubble sort and how do you perform it?

Answer: A bubble sort is one sorting technique that can be applied to data structures such as an array. 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 list, while the larger value sinks to the bottom.

Question-27: How does selection sort work?

Answer: Selection sort works by picking the smallest number from the list and placing it at the front. This process is repeated for the second position towards the end of the list. It is the simplest sort algorithm.

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Question-28: What is a graph?

Answer: A graph is one type of data structure that contains a set of ordered pairs. These ordered pairs are also referred to as edges or arcs, and are used to connect nodes where data can be stored and retrieved.

Question-29: What is an AVL tree?

Answer: An AVL tree is a type of binary search tree that is always in a state of partially balanced. The balance is measured as a difference between the heights of the sub-trees from the root. This self-balancing tree was known to be the first data structure to be designed as such.

Question-30: What is Huffman’s algorithm?

Answer: Huffman’s algorithm is associated in creating extended binary trees that has minimum weighted path lengths from the given weights. It makes use of a table that contains frequency of occurrence for each data element.

The above solved Data Structure Interview Questions will surely be helpful for you. Make your preparation stronger for Data Structure Interview round with the help of given questions and answers.

Some Important Things for You:

To crack the interview round, you need to make good command on your language, body posture, facial expressions and your confidence. Everything is important for you and gives you an advantage in interview round.

For Top 30 Data Structure Interview Questions & Answers, you need to look at above section which is well prepared by the team of recruitmentresult.com

Official Note:

We wish to say all the best to those aspirants who are going to attend Data Structure Interview round. You are supposed to prepare these top 30 Data Structure Interview Questions & Answers for cracking the interview.

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