Queues - Deletion of item from queue

Function Dequeue (Q)

The above Function deletes an element from the queue ‘Q’. Queue empty condition is checked by making a call to ‘IsEmpty’.

Step 1 Is Empty, call to IsEmpty

if (IsEmpty (Q)) then

message ‘Queue Empty’

return

else goto step 2.

Step 2 Deletion of an element

set temp ¬ Q (item [Q (front)])

Step 3 setting front and rear, if queue is empty

if Q (front) = Q(rear)) then

set Q (front) ¬ – 1

set Q (rear) ¬ – 1

else

set Q(front) ® Q(front) + 1

Step 4 return value at the time of call

return (temp)

Equivalent code is given below:

int Dequeue (queue* Q)

{

int temp

temp = Q ® item [Q ® front];

if (Q ® front = = Q ® rear)

Q ® front = Q ® rear = – 1;

else

Q ® front = Q ® front + 1;

return temp;

}