Data Structures

Which of the following is faster?

◦ A binary search of an ordered set of elements in

an array or a sequential search of the elements?

Question No : 1

The binary search is faster than the

sequential search.

◦ The complexity of binary search is 'log n' whereas

the complexity of a sequential search is 'n'.

◦ In a binary search, each time we proceed, we

have to deal with only half of the elements of the

array compared to the previous one. So the

search is faster.

Answer

List out the areas in which data structures

are applied extensively?

Question No : 2

Compiler Design

Operating System

Database Management

System

Statistical analysis package

Numerical Analysis

Graphics

Answer

Which data structure is used to perform

recursion?

Question No : 3

Stack.

◦ Because of its LIFO (Last In First Out) property it

remembers its caller and hence knows where to

return to when the function has to return.

◦ Recursion makes use of 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.

Answer

Tree can have duplicate values :

True (or) False?

Question No : 4

True

◦ Tree defines the structure of an acyclic graph but

does not disallow duplicates.

Answer

The size of a Tree is the number of nodes in

the Tree : True (or) False?

Question No : 5

True

◦ The size denotes the number of nodes, height

denotes the longest path from leaf node to root

node.

Answer

Ram is told to sort a set of Data using Data structure.

He has been told to use one of the following Methods

a. Insertion

b. Selection

c. Exchange

d. Linear

Now Ram says a Method from the above can not be

used to sort. Which is the method?

Question No : 6

d. Linear

◦ Using insertion we can perform insertion sort,

using selection we can perform selection sort, and

using exchange we can perform bubble sort.

◦ But no sorting method is possible using linear

method;

◦ Linear is a searching method

Answer

Ashok is told to manipulate an Arithmetic

Expression. What is the data structure he

will use?

a. Linked List

b. Tree

c. Graph

d. Stack

Question No : 7

d. Stack

Stacks are used to evaluate the algebraic or arithmetic

expressions using prefix or postfix notations

Answer

There are 8,15,13,14 nodes in 4 different

trees. Which of them could form a full

binary tree?

a. 8

b. 15

c. 13

d. 14

Question No : 8

In general, there are 2n – 1 nodes in a full

binary tree.

By the method of elimination: Full binary tree contains

odd number of nodes.

So there cannot be a full binary tree with 8 or 14 nodes.

With 13 nodes, you can form a complete binary tree but

not a full binary tree.

Full and complete binary trees are different

All full binary trees are complete binary trees but not

vice versa

Answer

Full binary Tree:

A binary tree is a full binary tree if and only if:

Each non leaf node has exactly two child nodes

All leaf nodes have identical path length

It is called full since all possible node slots are

occupiedA

B C

D E F G

Answer

Complete binary Tree:

A complete binary tree (of height h) satisfies the

following conditions:

Level 0 to h-1 represent a full binary tree of height h-1

One or more nodes in level h-1 may have 0, or 1 child

nodes

Answer

A

B C

D E F G

H I J K

How many null branches are there in a

binary tree with 20 nodes?

Question No : 9

21 (null branches)

Let’s consider a tree with 5 nodes

So the total number of null nodes in a binary tree of n

nodes is n+1

Answer

Null branches

Write an algorithm to detect loop in a linked

list.

You are presented with a linked list, which may have a

"loop" in it. That is, an element of the linked list may

incorrectly point to a previously encountered element,

which can cause an infinite loop when traversing the list.

Devise an algorithm to detect whether a loop exists in a

linked list. How does your answer change if you cannot

change the structure of the list elements?

Question No : 10

One possible answer is to add a flag to each element of

the list.

You could then traverse the list, starting at the head and

tagging each element as you encounter it.

If you ever encountered an element that was already

tagged, you would know that you had already visited it

and that there existed a loop in the linked list.

What if you are not allowed to alter the structure of the

elements of the linked list?

Answer

The following algorithm will find the loop:

a) Start with two pointers ptr1 and ptr2.

b) Set ptr1 and ptr2 to the head of the linked list.

c) Traverse the linked list with ptr1 moving twice as fast as ptr2

(for every two elements that ptr1 advances within the list,

advance ptr2 by one element).

d) Stop when ptr1 reaches the end of the list, or when ptr1 = ptr2.

e) If ptr1 and ptr2 are ever equal, then there must be a loop in the

linked list. If the linked list has no loops, ptr1 should reach the

end of the linked list ahead of ptr2

Answer

The Operation that is not allowed in a

binary search tree is

a. Location Change

b. Search

c. Deletion

d. Insertion

Question No : 11

a. Location Change

Answer

Array is a type of ________________ data

structure.

a. Non Homogenous

b. Non Linear

c. Homogenous but not Linear

d. Both Homogenous and Linear

Question No : 12

d. Both Homogenous and Linear.

Answer

The address of a node in a data structure is

called

a. Pointer

b. Referencer

c. Link

d. All the above

Question No : 13

d. All the above

Answer

The minimum number of edges in a

connected cycle graph on n vertices is

________

a. n

b. n + 1

c. n – 1

d. 2n

Question No : 14

a. n

Answer

The total number of passes required in a

selection sort is

a. n + 1

b. n – 1

c. n

d. n * n

Question No : 15

b. n – 1

Answer

The node that does not have any sub trees

is called ___________

a. Null Node

b. Zero Node

c. Leaf Node

d. Empty Node

Question No : 16

c. Leaf Node

Answer

Linked List is a

a. Static Data Structure

b. Primitive Data Structure

c. Dynamic Data Structure

d. None of the above

Question No : 17

c. Dynamic Data Structure

Answer

Which data structure is needed to convert

infix notation to postfix notation.

a. Tree

b. Linear Linked List

c. Stack

d. Queue

Question No : 18

c. Stack

Answer

If every node u in Graph (G) is adjacent to

every other node v in G, it is called as _____

graph.

a. Directed Graph

b. Complete Graph

c. Connected Graph

d. Multi Graph

Question No : 19

b. Complete Graph

Answer

Bubble sort is an example of

a. Selection sort technique

b. Exchange sort technique

c. Quick sort technique

d. None of the options

Question No : 20

b. Exchange sort technique

Answer

How do you chose the best algorithm

among available algorithms to solve a

problem

a. Based on space complexity

b. Based on programming requirements

c. Based on time complexity

d. All the above

Question No : 21

d. All the above

Answer

Which of the following are called

descendants?

a. All the leaf nodes

b. Parents, grandparents

c. Root node

d. Children, grandchildren

Question No : 22

d. Children, grandchildren

Answer

Choose the limitation of an array from the

below options.

a. Memory Management is very poor

b. Searching is slower

c. Insertion and deletion are costlier

d. Insertion and Deletion is not possible

Question No : 23

c. Insertion and deletion are costlier

◦ (It involves shifting rest of the elements)

Answer

Areas where stacks are popularly used are.

a. Subroutines

b. Expression Handling

c. Recursion

d. All the above

Question No : 24

d. All the above

Answer

How would you implement queue using

stack(s)?

Question No : 25

Use a temp stack

Data In into queue

◦ Push the element into the original stack

Data Out from queue

◦ Pop all the elements from stack into a temp stack

pop out the first element from the temp stack

Answer

Write a C program to compare two linked

lists.

Question No : 26

int

compare_linked_lists(struct

node *q, struct node *r){

static int flag;

if((q==NULL ) && (r==NULL)){

flag=1;

}

else{

if(q==NULL || r==NULL){

flag=0;

}

if(q->data!=r->data){

flag=0;

}

else{

compare_linked_lists(q-

>link,r->link);

}

}

return(flag);

}

Answer

Write a C program to return the nth node

from the end of a linked list.

Question No : 27

Suppose one needs to get to the 6th node from the end in the LL.

First, just keep on incrementing the first pointer (ptr1) till the number

of increments cross n (which is 6 in this case)

STEP 1 : 1(ptr1,ptr2) -> 2 -> 3 -> 4 -> 5 -> 6 -> 7 -> 8 -> 9 -> 10

STEP 2 : 1(ptr2) -> 2 -> 3 -> 4 -> 5 -> 6(ptr1) -> 7 -> 8 -> 9 -> 10

Now, start the second pointer (ptr2) and keep on incrementing it till

the first pointer (ptr1) reaches the end of the LL.

◦ STEP 3 : 1 -> 2 -> 3 -> 4(ptr2) -> 5 -> 6 -> 7 -> 8 -> 9 -> 10 (ptr1)

So here you have the 6th node from the end pointed to by ptr2!

Answer

struct node {

int data;

struct node *next;

}mynode;

mynode * nthNode(mynode *head, int n /*pass 0 for last node*/) {

mynode *ptr1,*ptr2;

int count;

if(!head) {

return(NULL);

}

ptr1 = head;

ptr2 = head;

count = 0;

Answer

while(count < n) {

count++;

if((ptr1=ptr1->next)==NULL) {

//Length of the linked list less than n. Error.

return(NULL);

} }

while((ptr1=ptr1->next)!=NULL) {

ptr2=ptr2->next;

}

return(ptr2);

}

Answer

Write a C program to insert nodes into a

linked list in a sorted fashion?

Question No : 28

Answer

// Special case code for the head endvoid linkedListInsertSorted(struct node** headReference, struct node* newNode){// Special case for the head endif (*headReference == NULL || (*headReference)->data >= newNode->data){newNode->next = *headReference;

The solution is to iterate down the list looking for the correct place to

insert the new node. That could be the end of the list, or a point just

before a node which is larger than the new node.

Let us assume the memory for the new node has already been

allocated and a pointer to that memory is being passed to this

function.

Answer

*headReference = newNode;}

else {

// Locate the node before which the insertion is to happen!

struct node* current = *headReference;

while (current->next!=NULL && current->next->data < newNode->data){

current = current->next;

}

newNode->next = current->next;

current->next = newNode;

}

}

Write a C program to remove duplicates

from a sorted linked list?

Question No : 29

Answer

// Remove duplicates from a sorted list

void RemoveDuplicates(struct node* head) {

struct node* current = head;

if (current == NULL) return; // do nothing if the list is empty

// Compare current node with next node

while(current->next!=NULL)

{

As the linked list is sorted, we can start from the beginning of

the list and compare adjacent nodes.

When adjacent nodes are the same, remove the second one.

There's a tricky case where the node after the next node

needs to be noted before the deletion.

Answer

if (current->data == current->next->data)

{

struct node* nextNext = current->next->next;

free(current->next);

current->next = nextNext;

}

else

{

current = current->next; // only advance if no

deletion

}

}

}

Write a C program to find the depth or

height of a tree.

Question No : 30

Answer

#define max(x,y) ((x)>(y)?(x):(y))

struct Bintree {

int element;

struct Bintree *left;

struct Bintree *right;

};

typedef struct Bintree* Tree;

int height(Tree T) {

if(!T)

return -1;

else

return (1 + max(height(T->left), height(T->right)))

}

Write C code to determine if two trees are

identical

Question No : 31

Answer

struct Bintree {

int element;

struct Bintree *left;

struct Bintree *right;

};

typedef struct Bintree* Tree;

int CheckIdentical( Tree T1, Tree T2 )

{

if(!T1 && !T2) // If both tree are NULL then return true

return 1;

Answer

else if((!T1 && T2) || (T1 && !T2)) //If either of one is

NULL, return false

return 0;

else

return ((T1->element == T2->element) &&

CheckIdentical(T1->left, T2-i>left)

&& CheckIdentical(T1->right, T2->right));

// if element of both tree are same and left and right

tree is also same then both

trees are same

}

Write a C code to create a copy of a Tree

Question No : 32

Answer

mynode *copy(mynode *root)

{

mynode *temp;

if(root==NULL)return(NULL);

temp = (mynode *) malloc(sizeof(mynode));

temp->value = root->value;

temp->left = copy(root->left);

temp->right = copy(root->right);

return(temp);

}

Which of the following are called siblingsa. Children of the same parent

b. All nodes in the given path upto leaf node

c. All nodes in a sub tree

d. Children, Grand Children

Question No : 33

a. Children of the same parent

Answer

Linked List can grow and shrink in size

dynamically at __________ .

a. Runtime

b. Compile time

Question No : 34

a. Runtime

Answer

The postfix of A+(B*C) is

a. ABC*+

b. AB+C*

c. ABC+*

d. +A*BC

Question No : 35

a. ABC*+

Answer

Data structure using sequential allocation is

called

a. Linear Data Structure

b. Non-Linear Data Structure

c. Non-primitive Data Structure

d. Sequence Data Structure

Question No : 36

a. Linear Data Structure

Answer

A linear list in which elements can be added

or removed at either end but not in the

middle is known as

a. Tree

b. Queue

c. Dequeue

d. Stack

Question No : 37

a. Dequeue

Answer

The average number of key comparisons

done in a successful sequential search in list

of length n is

a. n+1/2

b. n-1/2

c. n/2

d. log n

Question No : 38

a. n+1/2

Answer

A full binary tree with n leaves contains

__________

a. nlog2n nodes

b. 2^n nodes

c. (2n-1) nodes

d. n nodes

Question No : 39

c. (2n-1) nodes

Answer

If a node has positive outdegree and zero

indegree, it is called a __________.

a. Source

b. Sink

c. outdegree node

d. indegree node

Question No : 40

a. Source

Answer

The postfix notation for ((A+B)^C-(D-

E)^(F+G)) is

a. AB + C*DE—FG+^

b. ^-*+ABC –DE + FG

c. ^+AB*C—DE^+FG

d. ABC + CDE *-- FG +^

Question No : 41

a. AB + C*DE—FG+^

Answer

If you are using C language to implement

the heterogeneous linked list, what pointer

type will you use?

Question No : 42

The heterogeneous linked list contains

different data types in its nodes and we

need a pointer to connect them.

It is not possible to use ordinary pointers

for this.

So we use void pointer.

Void pointer is capable of storing pointer to

any

type of data (eg., integer or character) as it

is a generic pointer type.

Answer

What is heap sort?

Question No : 43

A Heap is an almost complete binary tree. In this tree, if the

maximum level is i, then, upto the (i-1)th level should be complete.

At level i, the number of nodes can be less than or equal to 2^i. If

the number of nodes is less than 2^i, then the nodes in that level

should be completely filled, only from left to right

The property of an ascending heap is that, the root is the lowest

and given any other node i, that node should be less than its left

child and its right child. In a descending heap, the root should be

the highest and given any other node i, that node should be

greater than its left child and right child.

Answer

To sort the elements, one should create the heap first. Once

the heap is created, the root has the highest value. Now we

need to sort the elements in ascending order. The root can not

be exchanged with the nth element so that the item in the nth

position is sorted. Now, sort the remaining (n-1) elements. This

can be achieved by reconstructing the heap for (n-1) elements.

Answer

heapsort() {

n = array(); // Convert the tree

into an array.

makeheap(n); // Construct the

initial heap.

for(i=n; i>=2; i--) {

swap(s[1],s[i]);

heapsize--;

keepheap(i);

}

}

makeheap(n) {

heapsize=n;

for(i=n/2; i>=1; i--)

keepheap(i);

}

keepheap(i) {

l = 2*i;

r = 2*i + 1;

p = s[l];

q = s[r];

t = s[i];

Answer

Answer

if(l<=heapsize && p->value > t->value)

largest = l;

else

largest = i;

m = s[largest];

if(r<=heapsize && q->value > m->value)

largest = r;

if(largest != i) {

swap(s[i], s[largest]);

keepheap(largest);

}

}

Implement the bubble sort algorithm. How

can it be improved? Write the code for

selection sort, quick sort, insertion sort.

Question No : 44

Bubble sort algorithm

Answer

void bubble_sort(int a[], int n){ int i, j, temp; for(j = 1; j < n; j++) { for(i = 0; i < (n - j); i++) { if(a[i] >= a[i + 1]) { //Swap a[i], a[i+1] } } }}

void bubble_sort(int a[], int n){ int i, j, temp; int flag; for(j = 1; j < n; j++) { flag = 0; for(i = 0; i < (n - j); i++) { if(a[i] >= a[i + 1]) { //Swap a[i], a[i+1] flag = 1; } } if(flag==0)break; }}

To improvise this basic algorithm, keep track of whether a particular pass results in any swap or not.

If not, you can break out without wasting more cycles.

Answer

Selection Sort Algorithm

void selection_sort(int a[],

int n) {

int i, j, small, pos, temp;

for(i = 0; i < (n - 1); i++)

{

small = a[i];

pos = i;

for(j = i + 1; j < n; j++)

{

if(a[j] < small)

{

small = a[j];

pos = j;

}

}

temp = a[pos];

a[pos] = a[i];

a[i] = temp;

}

}

Answer

Quick Sort Algorithm

int partition(int a[], int low, int high)

{

int i, j, temp, key;

key = a[low];

i = low + 1;

j = high;

while(1) {

while(i < high && key >= a[i])i++;

while(key < a[j])j--;

if(i < j) {

temp = a[i];

a[i] = a[j];

a[j] = temp;

}

else {

temp = a[low];

a[low] = a[j];

a[j] = temp;

return(j);

}

}

}

Answer

Answer

void quicksort(int a[], int low, int high) {

int j;

if(low < high) {

j = partition(a, low, high);

quicksort(a, low, j - 1);

quicksort(a, j + 1, high);

}

}

int main() {

// Populate the array a

quicksort(a, 0, n - 1);

}

Insertion Sort Algorithm

Answer

void insertion_sort(int a[], int n){ int i, j, item; for(i = 0; i < n; i++) { item = a[i]; j = i - 1; while(j >=0 && item < a[j]) { a[j + 1] = a[j]; j--; } a[j + 1] = item; }}