UGC NET CSE | December 2005 | Part 2 | Question: 24

Question

The initial configuration of quaue is $a, b, c, d$. $'a'$ is at the front. To get the configuration $d, c, b, a$ how many deletions and additions required:

• A. $2$ deletions, $3$ additions
• B. $3$ deletions, $2$ additions
• C. $3$ deletions, $4$ additions
• D. $3$ deletions, $3$ additions

Answer 1

To perform insertion and deletion in queue we have 2 variable called $\text{Front, Rear.}$

1. Front:  Front is a variable which contain position of element to be deleted.
2. Rear: Rear is a variable which contain position of element to be inserted.

Now according to the current queue: 

$a$ (front)

$b$

$c$

$d$

Delete $a$:

$-$

$b$ (front)

$c$

$d$

Delete $b$:

$-$

$-$

$c$(front)

$d$

Delete $c$:

$-$

$-$

$-$

$d$ (front,rear)

 

to achieve $d,c,b,a$ we have to perform 3 insertion;

Insert $c$:

$d$ (front)

$c$ (Rear)

Insert $b$:

$d$(front)

$c$

$b$(rear)

insert $a$:

$d$(front)

$c$

$b$

$a$(rear)

To get configuration $d,c,b,a$ we required $3$ deletion and $3$ insertion operation.

So option $D$ is correct.