Priority Queue

Description:-
This is a complete program of priority queue using single linked list.
Priority queue is a queue where value is inserted sequentially based on its priority.
So here the structure contain two int type fields named "priority" & "info" & there is a link which hold the address of the next structure type node.

Process:-
1. Copy the entire source code(Bold in format).
2. Paste that in your c or c++ compiler.
3. Save that with a suitable name.
4. Compile that program.
5. Finally run that program.

Error handling:-
Due to inappropriate html coding done by this web page I can't give the header file
name like stdio.h, conio.h, stdlib.h, iostream.h, fstream.h, iomanip.h etc.
If u get an error report after compiling the program
"CALL TO UNDEFINED FUNCTION 'PRINTF(OR ANYTHING)' IN FUNCTION MAIN()"
please add the above mentioned header file after #include
like #include.

Disclaimer:-
If you have any other problem regarding the program please mail me.
My mail address is showing on my blog page.

Source code:-


/* Program of priority queue using linked list*/
#include
#include
#include
struct node
{
int priority;
int info;
struct node *link;
}*front = NULL;

main()
{
int choice;
while(1)
{
printf("1.Insert\n");
printf("2.Delete\n");
printf("3.Display\n");
printf("4.Quit\n");
printf("Enter your choice : ");
scanf("%d", &choice);
switch(choice)
{
case 1:
insert();
break;
case 2:
del();
break;
case 3:
display();
break;
case 4:
exit(1);
default :
printf("Wrong choice\n");
}/*End of switch*/
}/*End of while*/
}/*End of main()*/

insert()
{
struct node *tmp,*q;
int added_item,item_priority;
tmp = (struct node *)malloc(sizeof(struct node));
printf("Input the item value to be added in the queue : ");
scanf("%d",&added_item);
printf("Enter its priority : ");
scanf("%d",&item_priority);
tmp->info = added_item;
tmp->priority = item_priority;
/*Queue is empty or item to be added has priority more than first item*/
if( front == NULL || item_priority <>priority )
{
tmp->link = front;
front = tmp;
}
else
{
q = front;
while( q->link != NULL && q->link->priority <= item_priority ) q=q->link;
tmp->link = q->link;
q->link = tmp;
}/*End of else*/
}/*End of insert()*/

del()
{
struct node *tmp;
if(front == NULL)
printf("Queue Underflow\n");
else
{
tmp = front;
printf("Deleted item is %d\n",tmp->info);
front = front->link;
free(tmp);
}
}/*End of del()*/

display()
{
struct node *ptr;
ptr = front;
if(front == NULL)
printf("Queue is empty\n");
else
{ printf("Queue is :\n");
printf("Priority Item\n");
while(ptr != NULL)
{
printf("%5d %5d\n",ptr->priority,ptr->info);
ptr = ptr->link;
}
}/*End of else */
}/*End of display() */