| Every time we delete an element, we check whether
it is the last element left in the queue or not. If it is then we delete it and make
our 'front', 'rear' and 'queue' pointers to point to NULL; to depict an empty
queue. If the queue is empty, we give a "queue empty" message.
Algorithm:-
Step-1:
Check for the "queue empty" condition. If it is then go to
step-2 or else step-3
Step-2: Give away a "queue empty" message and quit
Step-3: Delete the element. If this was the last element to be
deleted then go to step-a or else step-b
step-a:
make our 'front', 'rear' and 'queue' pointers NULL
step-b:
shift your 'front' and 'queue' pointer ahead to point to the next
element in
the queue
C implementation:-
struct node
{
int value;
struct node *next;
}
struct node *queue, *front, *rear;
main( )
{
queue = front = rear = NULL; /*queue
is initially empty*/
..
..
del_value = delete( );
..
del_value = delete( );
..
}
int delete( )
{
int delval = 0;
if(front == NULL) printf("queue empty"); /*step-2*/
else
{
/*step-3*/
delval = front->value;
if(front->next == NULL)
{
free(front);
queue = front = rear = NULL; /*step-a*/
}
else /*step-b*/
{
front = front->next;
free(queue);
queue = front;
}
}
}
Related Operations:
Queues
- Concepts
Array implementation - add( ) and delete(
)
Linked List implementation - add( )
and delete( )
Circular queues - add( ) and delete(
)
|
