Interview Questions.

Data Structures Interview Questions and Answers


Data Structures Interview Questions and Answers

Q1. What is facts structure?

Ans: A statistics shape is a manner of organizing statistics that considers not only the objects saved, but also their courting to each different. Advance information approximately the connection among records items permits designing of efficient algorithms for the manipulation of records.

Q2. List out few of the Application of tree statistics-structure?


The manipulation of Arithmetic expression

Symbol Table creation

Syntax analysis.

Q3. What is a spanning Tree?

Ans: A spanning tree is a tree associated with a community. All the nodes of the graph appear at the tree as soon as. A minimal spanning tree is a spanning tree organized in order that the overall part weight between nodes is minimized.

Q4. What is a related listing?

Ans: Linked listing is a information shape which save same form of records elements however not in continuous memory places and length is not constant. The linked lists are associated logically.

Q5. What is a node?

Ans: The facts element of a connected listing is called a node.

Q6. What are precedence queues?

Ans: A priority queue is a collection of factors such that every detail has been assigned a concern.

Q7. What is a string?

Ans: A sequential array of characters is referred to as a string.

Q8. What is Brute Force algorithm?

Ans: Algorithm used to go looking the contents by means of evaluating each element of array is known as Brute Force set of rules.

Q9. What is the kind of the set of rules utilized in fixing the 8 Queens problem?

Ans: Backtracking.

Q10. In RDBMS, what is the efficient records structure used within the internal storage illustration?

Ans: B+ tree. Because in B+ tree, all of the records is saved simplest in leaf nodes, that makes looking simpler. This corresponds to the facts that shall be stored in leaf nodes.

Q11.  How can you conquer the restrictions of arrays?

Ans: Limitations of arrays may be solved by way of the use of the linked list.

Q12. What does node consist of?

Ans: Node consists of two fields:facts area to shop the element and link field to store the address of the subsequent node.

Q13. What is a queue ?

Ans: A Queue is a sequential agency of facts. A queue is a primary in first out type of facts shape. An detail is inserted on the ultimate function and an detail is continually taken out from the primary function.

Q14. What are the types of Collision Resolution Techniques and the methods used in each of the kind?

Ans: Open addressing (closed hashing),The techniques used include:Overflow block.

Closed addressing (open hashing),The techniques used include:Linked list,Binary tree.

Q15. What are the methods available in storing sequential documents?

Ans: Straight merging, Natural merging, Polyphase kind, Distribution of Initial runs.

Q16. Mention some of the hassle fixing strategies?

Ans: The maximum widely strategies are listed underneath:

Divide and overcome

Binary doubling method

Dynamic programming

Q17. Minimum quantity of queues had to put in force the priority queue?

Ans: Two. One queue is used for real storing of information and any other for storing priorities.

Q18. What are the notations used in Evaluation of Arithmetic Expressions the use of prefix and postfix forms?

Ans: Polish and Reverse Polish notations.

Q19.  List out the regions wherein statistics systems are implemented appreciably?

Ans: Compiler Design, Operating System, Database Management System, Statistical

analysis bundle, Numerical Analysis, Graphics, Artificial Intelligence, Simulation

Q20. Translate infix expression into its equal put up repair expression: (A-B)*(D/E)

Ans: (A-B)*(D/E) = [AB-]*[DE/] = AB-DE/*

Q21. What are the restrictions of arrays?


Arrays are of fixed length.

Data elements are stored in continuous reminiscence places which may not be available usually.

Adding and disposing of of elements is difficult due to shifting the places.

Q22. What are the packages of binary tree?

Ans: Binary tree is used in statistics processing.

Q23. What are the different styles of traversing?

Ans: The one-of-a-kind types of traversing are:

Pre-order traversal-yields prefix from of expression.

In-order traversal-yields infix shape of expression.

Post-order traversal-yields postfix from of expression.

Q24. Define pre-order traversal?


Process the foundation node

Process the left subtree

Process the proper subtree

Q25. Define post-order traversal?


Process the left subtree

Process the right subtree

Process the root node

Q26. Define in -order traversal?


Process the left subtree

Process the root node

Process the right subtree

Q27. What actions are carried out while a function is called?


Arguments are passed

Local variables are allotted and initialized

Transferring control to the characteristic

Q28. What is precision?

Ans: Precision refers the accuracy of the decimal portion of a cost. Precision is the variety of digits allowed after the decimal factor.

Q29. What is meant through sorting?

Ans: Ordering the data in an growing or reducing style in step with a few courting the various statistics item is known as sorting.

Q30. What's the predominant distinction in between Storage shape and record shape and how?

Ans: The expression of an particular records shape interior memory of a computer device is termed garage shape in assessment to a garage shape expression in auxiliary reminiscence is generally called a report structure.

Q31. What is divide and triumph over method?

Ans: The fundamental concept is to divide the hassle into several sub troubles beyond which can not be in addition subdivided. Then resolve the sub issues correctly and be a part of then together to get the answer for the main problem.

Q32. What is suggest through d-queue?

Ans: D-queue stands for double ended queue. It is a summary information shape that implements a queue for which factors may be introduced to front or rear and the factors can be removed from the rear or the front. It is likewise referred to as head-tail connected list

Q33. What is AVL tree?

Ans: Avl tree is self binary tree in which balancing element lie among the -1 to one. It is likewise referred to as self balancing tree.

Q34. What is binary tree?

Ans: Binary tree is a tree which has maximum no. Of youngsters both zero or 1 or 2. I.E., there is on the most 2 branches in every node.

Q35. What is the need for the header?

Ans: Header of the related listing is the primary element inside the list and it stores the quantity of elements within the list. It points to the primary information detail of the list.

Q36. Define leaf?

Ans: In a directed tree any node which has out diploma o is referred to as a terminal node or a leaf.

Q37. Stack may be defined as a pointer. Explain?

Ans: Because stack will include a head pointer as a way to usually point to the pinnacle of the Stack.All Stack Operations are achieved using Head Pointer. Hence Stack ca be Described as a Pointer

Q38. What do you imply through: Syntax Error, Logical Error, Run time Error? 

Ans: Syntax Error-Syntax Error is because of lack of know-how in a particular language. It is because of somebody does not know the way to use the capabilities of a language.We can know the errors on the time of compilation.

Logical Error-It is due to the poor know-how of the requirement or hassle.

Run time Error-The exceptions like divide a variety of by means of zero,overflow and underflow comes beneath this.

Q39. What is the distinction between a stack and a Queue?


Stack: Represents the gathering of factors in Last In First Out order. Operations consists of trying out null stack, locating the top detail within the stack, elimination of pinnacle maximum element and adding factors on the top of the stack.

Queue: Represents the collection of factors in First In First Out order.Operations consist of testing null queue, locating the next detail, elimination of factors and putting the factors from the queue.

Insertion of factors is at the end of the queue.Deletion of factors is from the start of the queue

Q40. What do you imply through overflow and underflow? 

Ans: When new statistics is to be inserted into the information shape but there may be no to be had area i.E.Unfastened garage list is empty this situation is referred to as overflow.When we want to delete records from a data structure that is empty this example is known as underflow.

Q41. Is it possible to discover a loop in a Linked listing?


Possilbe at O(n)

Not feasible

Possible at O(n^2) simplest

Depends on the location of loop

Solution: a. Possible at O(n)

Have  tips say P1 and P2 pointing to the primary node of the list.

Start a loop and Increment P1 once and P2 two times in each new release. At any factor of time if P1==P2 then there may be a loop in that connected list. If P2 reaches NULL (cease of connected list) then no loop exists.

Q42. Two related lists L1 and L2 intersects at a particular node N1 and from there all other nodes till the stop are commonplace. The period of the lists are not equal. What are the possibilities to locate N1?


Solution exist for positive instances most effective

No linear solution exist

Linear answer is possible

Only Non-linear answer exist.

Solution: c. Linear answer is possible

Have  tips say P1 pointing to the first node of L1 and P2 to that of L2. Traverse thru each the lists. If P1 reaches L1’s final node, factor it to the first node of L2 and continue traversing. Do the same thing for P2 whilst it reaches L2’s last node. (By doing this, we are balancing the difference inside the duration among the connected lists. The shorter one will recover from soon and by means of redirecting to longer listing’s head, it will traverse the more nodes additionally.) Finally they may Meet at the Intersection node.

Q43. Void PrintTree (Tree T)



if (T != NULL)

PrintTree (T-> Left);

PrintElement (T-> Element);

PrintTree (T->Right);


The above method ‘PrintTree’ effects wherein of the following traversal




None of the above

Solution: a. Inorder


void PrintTree (Tree T)

if (T != NULL)

PrintTree (T-> Left);

PrintElement (T-> Element);

PrintTree (T->Right);


For preorder use this order

PrintElement (T-> Element);

PrintTree (T-> Left);

PrintTree (T->Right);

For postorder use this order

PrintTree (T-> Left);

PrintTree (T->Right);

PrintElement (T-> Element);


Q44. Given a Binary Search Tree (BST), print its values in ascending order.


Perform Depth first traversal

Perform Breadth first traversal

Perform Postorder traversal

Perform Inorder traversal

Solution: d. Perform Inorder traversal

It is the properfy of BST and Inorder traversal.

Q45. Is it viable to put in force a queue the usage of Linked List ?. Enqueue & Dequeue ought to be O(1).


Not possible to put in force.

Only Enqueue is viable at O(1).

Only Dequeue is viable at O(1).

Both Enqueue and Dequeue is feasible at O(1)

Solution: d. Both Enqueue and Dequeue is feasible at O(1)

Have two pointers H pointing to the Head and T pointing to the Tail of the linked listing. Perform enqueue at T and perform dequeue at H. Update the guidelines after every operations hence.

Q46. Given a Tree, is it possible to find the best and least amongst leaves in linear time?


Solution relies upon at the tree structure

Linear answer exist

Only Non-linear answer exist.

No linear answer exist

Solution: b. Linear solution exist

Have  variables Min and Max. Perform any tree traversal.Assign the primary traversed leaf element to Min and Max for all other leaf elements take a look at with those variables and replace it as a result. If a modern detail is < Min then update Min with that element. If it is > Min then check with Max.

Note: If you need to discover the finest and least amongst all nodes carry out the tests for every node traversed.

Q47. Is it possible to locate locate the greatest and least price many of the nodes in a given BST without the usage of any extra variables?


No answer exist.

Solution want 2 greater variables

Solution exist without any more variables

Solution need 1 extra variable

Solution:c Solution exist without any greater variables

As in keeping with BST property, the left most node should be the least one and the rightmost node have to be the greatest. In different phrases, the first and closing node of an Inorder traversal are the least and finest a few of the nodes respectively.

Q48. Is it possible to implement 2 stack in an array?

Ans: Condition: None of the stack ought to imply an overflow until every slot of an array is used.

Only 1 stack can be applied for the given situation

Stacks cannot be implemented in array

2 stacks can be carried out for the given circumstance.

2 stacks may be carried out if the given condition is carried out simplest for 1 stack.

Solution:c. 2 stacks may be implemented for the given situation

Start 1st stack from left (1st role of an array) and 2d from right (last function say n). Move 1st stack towards right( i.E 1,2,3 ...N) and second closer to left (i.E n,n-1,n-2...1).

Q49. Given  keys K1 & K2, write an set of rules to print all of the elements among them with K1<=K2 in a BST.


Solution need 2 extra spaces

Linear solution is viable without the use of any greater area

No linear solution exist

Solution need 1 extra space

Solution: Linear solution is feasible without using any more space

Perform an inorder traversal. Once you find K1 print it and retain traversal now, print all other traversed elements until you reach K2.

Note: If K1 == K2 stop when you locate K1.

Q50. How many stacks are required to implement a Queue?





Two + one greater area.

Solution: Two

Have two stacks S1 and S2.

For Enqueue, perform push on S1.

For Dequeue, if S2 is empty pop all of the factors from S1 and push it to S2. The final detail you popped from S1 is an detail to be dequeued. If S2 isn't always empty, then pop the pinnacle element in it.