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1)What is data-structure?
Data structure is a way of defining, storing and retriving of data in a structural and systemetic way. A data structure may contain different type of data items.

2)What are various data-structures available?
Data structure availability may vary by programming languages. Commonly available data structures are list, arrays, stack, queues, graph, tree etc.

3)What is selection sort?
Selection sort is in-place sorting technique. It divides the data set into two sub-lists: sorted and unsorted. Then it selects the minimum element from unsorted sub-list and places it into the sorted list. This iterates unless all the elements from unsorted sub-list are consumed into sorted sub-list.

4)How insertion sort and selection sorts are different?
Both sorting techniques maintains two sub-lists, sorted and unsorted and both take one element at a time and places it into sorted sub-list. Insertion sort works on the current element in hand and places it in the sorted array at appropriate location maintaining the properties of insertion sort. Whereas, selection sort searches the minimum from the unsorted sub-list and replaces it with the current element in hand.

5)What is merge sort and how it works?
Merge sort is sorting algorithm based on divide and conquer programming approach. It keeps on dividing the list into smaller sub-list until all sub-list has only 1 element. And then it merges them in a sorted way until all sub-lists are consumed. It has run-time complexity of Ο(n log n) and it needs Ο(n) auxiliary space.

6)What is shell sort?
Shell sort can be said a variant of insertion sort. Shell sort divides the list into smaller sublist based on some gap variable and then each sub-list is sorted using insertion sort. In best cases, it can perform upto Ο(n log n).

7)Briefly explain the approaches to develop algorithms.
There are three commonly used approaches to develop algorithms Greedy Approach− finding solution by choosing 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

8)Give some examples greedy algorithms.
The below given problems find their solution using greedy algorithm approach Travelling Salesman Problem Prim's Minimal Spanning Tree Algorithm Kruskal's Minimal Spanning Tree Algorithm Dijkstra's Minimal Spanning Tree Algorithm Graph - Map Coloring Graph - Vertex Cover Knapsack Problem Job Scheduling Problem

9)What are some examples of divide and conquer algorithms?
The below given problems find their solution using divide and conquer algorithm approach Merge SortQuick SortBinary Search Strassen's Matrix MultiplicationClosest pair (points)

10)What are some examples of dynamic programming algorithms?
The below given problems find their solution using divide and conquer algorithm approach Fibonacci number series Knapsack problem Tower of Hanoi All pair shortest path by Floyd-Warshall Shortest path by Dijkstra Project scheduling

11)What is a linked-list?
A linked-list is a list of data-items connected with links i.e. pointers or references. Most modern high-level programming language does not provide the feature of directly accessing memory location, therefore, linked-list are not supported in them or available in form of inbuilt functions.

12)What is stack?
In data-structure, stack is an Abstract Data Type (ADT) used to store and retrieve values in Last In First Out method.

13)Why do we use stacks?
Stacks follows LIFO method and addition and retrieval of a data item takes only Ο(n) time. Stacks are used where we need to access data in the reverse order or their arrival. Stacks are used commonly in recursive function calls, expression parsing, depth first traversal of graphs etc.

14)What operations can be performed on stacks?
The below operations can be performed on a stack − push() : adds an item to stack pop() : removes the top stack item peek() : gives value of top item without removing it isempty(): checks if stack is empty isfull() : checks if stack is full

15)What is a queue in data-structure?
Queue is an abstract data structure, somewhat similar to stack. In contrast to stack, queue is opened at both end. One end is always used to insert data (enqueue) and the other is used to remove data (dequeue). Queue follows First-In-First-Out methodology, i.e., the data item stored first will be accessed first.

16)Why do we use queues?
As queues follows FIFO method, they are used when we need to work on data-items in exact sequence of their arrival. Every operating system maintains queues of various processes. Priority queues and breadth first traversal of graphs are some examples of queues.

17)What operations can be performed on Queues?
The below operations can be performed on a stack − enqueue() : adds an item to rear of the queue dequeue() : removes the item from front of the queue peek() : gives value of front item without removing it isempty() : checks if stack is empty isfull() : checks if stack is full

18)What is linear searching?
Linear search tries to find an item in a sequentially arranged data type. These sequentially arranged data items known as array or list, are accessible in incrementing memory location. Linear search compares expected data item with each of data items in list or array. The average case time complexity of linear search is Ο(n) and worst case complexity is Ο(n2). Data in target arrays/lists need not to be sorted.

19)What is binary search?
A binary search works only on sorted lists or arrays. This search selects the middle which splits the entire list into two parts. First the middle is compared. This search first compares the target value to the mid of the list. If it is not found, then it takes decision on whether.

20)What is bubble sort and how bubble sort works?
Bubble sort is comparison based algorithm in which each pair of adjacent elements is compared and elements are swapped if they are not in order. Because the time complexity is Ο(n2), it is not suitable for large set of data.

21)Tell me something about 'insertion sort'?
Insertion sort divides the list into two sub-list, sorted and unsorted. It takes one element at time and finds it appropriate location in sorted sub-list and insert there. The output after insertion is a sorted sub-list. It iteratively works on all the elements of unsorted sub-list and inserts them to sorted sub-list in order.

22)How quick sort works?
Quick sort uses divide and conquer approach. It divides the list in smaller 'partitions' using 'pivot'. The values which are smaller than the pivot are arranged in the left partition and greater values are arranged in the right partition. Each partition is recursively sorted using quick sort.

23)What is a graph?
A graph is a pictorial representation of a set of objects where some pairs of objects are connected by links. The interconnected objects are represented by points termed as vertices, and the links that connect the vertices are called edges.

24)How depth first traversal works?
Depth First Search algorithm(DFS) traverses a graph in a depthward motion and uses a stack to remember to get the next vertex to start a search when a dead end occurs in any iteration.

25)How breadth first traversal works?
Breadth First Search algorithm(BFS) traverses a graph in a breadthwards motion and uses a queue to remember to get the next vertex to start a search when a dead end occurs in any iteration.

26)What is a tree?
A tree is a minimally connected graph having no loops and circuits.

27)What is a binary tree?
A binary tree has a special condition that each node can have two children at maximum.

28)What is a binary search tree?
A binary search tree is a binary tree with a special provision where a node's left child must have value less than its parent's value and node's right child must have value greater than it's parent value.

29)What is tree traversal?
Tree traversal is a process to visit all the nodes of a tree. Because, all nodes are connected via edges (links) we always start from the root (head) node. There are three ways which we use to traverse a tree In-order TraversalPre-order TraversalPost-order Traversal

30)What is an AVL Tree?
AVL trees are height balancing binary search tree. AVL tree checks the height of left and right sub-trees and assures that the difference is not more than 1. This difference is called Balance Factor. BalanceFactor=height(left-sutree) − height(right-sutree)

31)What is a spanning tree?
A spanning tree is a subset of Graph G, which has all the vertices covered with minimum possible number of edges. A spanning tree does not have cycles and it can not be disconnected.

32)How many spanning trees can a graph has?
It depends on how connected the graph is. A complete undirected graph can have maximum nn-1 number of spanning trees, where n is number of nodes.

33)How Kruskal's algorithm works?
This algorithm treats the graph as a forest and every node it as an individual tree. A tree connects to another only and only if it has least cost among all available options and does not violate MST properties.

34)How Prim's algorithm finds spanning tree?
Prim's algorithm treats the nodes as a single tree and keeps on adding new nodes to the spanning tree from the given graph.

35)What is a minimum spanning tree (MST) ?
In a weighted graph, a minimum spanning tree is a spanning tree that has minimum weight that all other spanning trees of the same graph.

36)What is a heap in data structure?
Heap is a special balanced binary tree data structure where root-node key is compared with its children and arranged accordingly. A min-heap, a parent node has key value less than its childs and a max-heap parent node has value greater than its childs.

37)What is a recursive function?
A recursive function is one which calls itself, directly or calls a function that in turn calls it. Every recursive function follows the recursive properties − base criteria where functions stops calling itself and progressive approach where the functions tries to meet the base criteria in each iteration.

38)What is algorithm?
Algorithm is a step by step procedure, which defines a set of instructions to be executed in certain order to get the desired output.

39)Why we need to do algorithm analysis?
A problem can be solved in more than one ways. So, many solution algorithms can be derived for a given problem. We analyze available algorithms to find and implement the best suitable algorithm.

40)What are the criteria of algorithm analysis?
An algorithm are generally analyzed on two factors − time and space. That is, how much execution time and how much extra space required by the algorithm.

41)What is asymptotic analysis of an algorithm?
Asymptotic analysis of an algorithm, refers to defining the mathematical boundation/framing of its run-time performance. Using asymptotic analysis, we can very well conclude the best case, average case and worst case scenario of an algorithm.

42)What are asymptotic notations?
Asymptotic analysis can provide three levels of mathematical binding of execution time of an algorithm − Best case is represented by Ο(n) notation.Worst case is represented by Ω(n) notation.Average case is represented by Θ(n) notation.

43)What is linear data strucutre?
A linear data-strucutre 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.

44)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

45) What pointer type is used to implement the heterogeneous linked list in C?
Void pointer. The heterogeneous linked list contains different data types in it's nodes and we need a link, pointer, to connect them. Since we can't use ordinary pointers for this, we use the void pointer. Void pointer is a generic pointer type, and capable of storing pointer to any type.

46) What is the minimum number of queues needed to implement the priority queue?
Two. One queue is used for the actual storing of data, and the other one is used for storing the priorities.

47)Which data structure is used to perform recursion?
The answer is Stack. Stack has the LIFO (Last In First Out) property; it remembers it's ‘caller’. Therefore, it knows to whom it should return when the function has to return. On the other hand, recursion makes use of the system stack for storing the return addresses of the function calls. Every recursive function has its equivalent iterative (non-recursive) function. Even when such equivalent iterative procedures are written explicit, stack is to be used.

48) What are some of the applications for the tree data structure?
Manipulation of the arithmetic expressions.Symbol table construction.Syntax analysis.

49)Which data strucutres algorithm used in solving the eight Queens problem?
Backtracking 50) In an AVL tree, at what condition the balancing is to be done?
If the "pivotal value", or the "height factor", is greater than one or less than minus one.

51) What is the bucket size, when the overlapping and collision occur at the same time?
The answer is one. If there is only one entry possible in the bucket, when the collision occurs, there is no way to accommodate the colliding value. This results in the overlapping of values.

52) There are 8, 15, 13, and 14 nodes in 4 different trees. Which one of them can form a full binary tree?
The answer is the tree with 15 nodes. In general, there are 2^n-1 nodes in a full binary tree. By the method of elimination: Full binary trees contain odd number of nodes, so there cannot be full binary trees with 8 or 14 nodes. Moreover, with 13 nodes you can form a complete binary tree but not a full binary tree. Thus, the correct answer is 15.

53)Whether Linked List is linear or Non-linear data structure?
According to Storage Linked List is a Non-linear one.

54) Is it necessary to sort a file before searching a particular item ?
If less work is involved in searching a element than to sort and then extract, then we don’t go for sort If frequent use of the file is required for the purpose of retrieving specific element, it is more efficient to sort the file. Thus it depends on situation.

55) What are the issues that hamper the efficiency in sorting a file?
The issues are : i) Length of time required by the programmer in coding a particular sorting program ii) Amount of machine time necessary for running the particular program iii)The amount of space necessary for the particular program .

56) Calculate the efficiency of sequential search?
The number of comparisons depends on where the record with the argument key appears in the table If it appears at first position then one comparison If it appears at last position then n comparisons Average=(n+1)/2 comparisons Unsuccessful search n comparisons Number of comparisons in any case is O (n).

57) Is any implicit arguments are passed to a function when it is called?
Yes there is a set of implicit arguments that contain information necessary for the function to execute and return correctly. One of them is return address which is stored within the function’s data area, at the time of returning to calling program he address is retrieved and the function branches to that location.

58) Parenthesis is never required in Postfix or Prefix expressions, why?
Parenthesis is not required because the order of the operators in the postfix /prefix expressions determines the actual order of operations in evaluating the expression

59)What is tower of hanoi?
Tower of Hanoi, is a mathematical puzzle which consists of three tower (pegs) and more than one rings. All rings are of different size and stacked upon each other where the large disk is always below the small disk. The aim is to move the tower of disk from one peg to another, without breaking its properties.

60)What is fibonacci series?
Fibonacci Series generates subsequent number by adding two previous numbers. For example − 0 1 1 2 3 5 8 13.

61)What is hashing?
Hashing is a technique to convert a range of key values into a range of indexes of an array. By using hash tables, we can create an associative data storage where data index can be find by providing its key values.

62)What is interpolation search technique?
Interpolation search is an improved variant of binary search. This search algorithm works on the probing position of required value.

63)What is the prefix and post fix notation of (a + b) * (c + d) ?
Prefix Notation − * + a b + c d Postfix Notation − a b + c d + *

Data structures