DSA - Queue

Question 1

what is DS

Answer 1

way to store and organize data

Question 3

is Queue linear DS

Answer 3

yea queue is linear data str

Question 4

is queue abstract DS

Answer 4

yes, queue is an abstract DS

Question 5

what is FIFO

Answer 5

first in first out

Question 6

what are operation on queue

Answer 6

enqueue, dequeue

Question 7

what is enqueue

Answer 7

inserting node from rear end is known as enquque

Question 8

what is dequeue

Answer 8

deleting node from front end part is known as dequeue

Question 9

what are front and rear

Answer 9

front and rear are two variables

Question 10

what does front part is used for

Answer 10

front part is used for deleting operation

Question 11

what is use of rear variable

Answer 11

we use rear variable to add data into the queue

Question 12

from which node we can insert data

Answer 12

we can insert data from rear end

Question 13

from which part we can delete data in queue

Answer 13

we can delete data from front part in queue

Question 14

suppose there are three variables, 2, 3, 4 where would front and rear point

Answer 14

front will point to 2 and
rear will point to 4, end of queue

Question 15

suppose there are three variables, 2, 3, 4 and now you want to insert data into queue, from where will you insert it

Answer 15

we can insert data into queue from rear end, which is pointing to last element

Question 16

whats the first step when inserting / enqueing element into queue

Answer 16

first we increment the variable, rear++
insert data => second step

Question 17

what is LILO

Answer 17

LILO is last in last out

Question 18

do we have to pass parameter into enqueue()

Answer 18

yes we have to pass data, we are inserting into enqueue() function

Question 19

do we have to pass anything into dequeue() function

Answer 19

no we dont have to pass anython into dequeue()

Question 20

why we dont pass anything into dequeue()

Answer 20

by default the element is getting deleted is from front part

Question 21

what is front() or peek() function

Answer 21

it gives us first element without deleting the element

Question 22

isFull()

Answer 22

this function will return true if queue is empty, else it will return false

Question 23

isEmpty()

Answer 23

if queue is empty this function will return true, else this function will return false

Question 24

for which values we initialize front and rear

Answer 24

we initialize front and rear to -1

Question 25

which variable we increment while doing enqueue()

Answer 25

we increment rear variable while insert elements

Question 26

which variable stays at the same position while inserting element to queue

Answer 26

front stays at its place while incrementing

Question 27

what happens when we dequeue an element

Answer 27

we increment the value value of front

Question 28

peek() returns what

Answer 28

peek() function returns position where front is pointintg

Question 29

when front and rear become equal

Answer 29

when there is only one element, then the front and rear points to the same position

Question 30

what is meaning of
#define n 5

Answer 30

define N, makes global variable and add 5 to it

Question 30

what is first thing we check into enqueue() function

Answer 30

first thing we check in enqueue() function, is that is queue is overflow or not

overflow means, is queue is full or not

Question 31

what are applications of queue

Answer 31

serving request from single source

in OS processes are placed into queue

Question 32

why we need to pass int x, to enqueue() function

Answer 32

into x, we are going to send information or data

Question 32

how to take array for queue

Answer 32

int queue[5];

we can use

int queue[N];

Question 32

take two variables and initialize them to -1

Answer 32

int front = -1;
int rear = -1;

Question 33

do we need to declare front and rear globally

Answer 33

yes, we have to declare front and rear globally

Question 33

define enqueue() function

Answer 33

void enqueue(int x) {}

Question 34

how to check overflow of queue

Answer 34

if(rear == N - 1) {
printf(“overflow or queue is full \n”);
}

Question 35

how to check this second condition

Answer 35

else if(rear == -1 && front == -1){

front = rear = 0;
queue[rear] = x;

}

Question 35

what is second we check in enqueue function

Answer 35

in enqueue function second thing we had to check is that, is queue is full empty or not, is that front and rear has -1 values, means that queue is not having any elementyet

Question 35

what is third case in enqueue function

Answer 35

in this third condition, queue is not empty, queue is not overflow or not full filled

we handle this in third case

Question 36

what to do, when queue is not full or queue is not completely empty.

write code for third condition…

Answer 36

else{
rear++;
queue[rear];
}

} // enqueue ends here

Question 36

what is first case we have to check in dequeue() function

Answer 36

first thing we have to check in dequeue function is that, is queue is empty or not

Question 36

declare dequeue function

Answer 36

void dequeue()’

Question 37

what if queue is empty when we call dequeue function

Answer 37

if we call dequeue function, then its underflow condition

Question 38

how to check if queue is empty or not, what variables we have to use

Answer 38

we have to use both front and rear variables to check if queue is empty or not

Question 39

how to write condition

Answer 39

if(front == -1 && rear == -1){
printf(“queue is empty that is underflow case \n”);
}

Question 39

what is second condition we have to check in dequeue function

Answer 39

if queue is having one element or not

Question 39

why do we write
front = rear = -1;
in second condition of dequeue function

Answer 39

if there is only element, then after deleting it, front and rear should be having -1 value into it

Question 39

how to check if queue is having only one element

Answer 39

else if(front == rear) {
front = rear = -1;
}

Question 40

what we check in third condition

Answer 40

if there are more than one element in queue

Question 40

write third condition for dequeue function

Answer 40

else{

front++;

}

Question 40

how to print dequeued element

Answer 40

before doing front++, we have to print element

Question 40

write code for displaying dequeued elemetn

Answer 40

void dequeue(){
// if queue is empty
// if queue has only one element
// more than one element

if(front == -1 && queue == -1){
// empty queue
} else if(front == rear) {
// one element only
front = rear = -1;
} else {
printf(%d”, queue[front]);
}

}

Question 40

why we write front++ in dequeue

Answer 40

to delete we have to increment the value of front variable