🚀 Programming Example
C Program of priority queue using a linked list
C Program of priority queue using a linked list
/* Program of priority queue using linked list*/
#include<stdio.h>
#include<stdlib.h>
struct node
{
int priority;
int info;
struct node *link;
}*front=NULL;
void insert(int item, int item_priority);
int del();
void display();
int isEmpty();
main()
{
int choice,item,item_priority;
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:
printf("Input the item to be added in the queue : ");
scanf("%d",&item);
printf("Enter its priority : ");
scanf("%d",&item_priority);
insert(item, item_priority);
break;
case 2:
printf("Deleted item is %d\n",del());
break;
case 3:
display();
break;
case 4:
exit(1);
default :
printf("Wrong choice\n");
}/*End of switch*/
}/*End of while*/
}/*End of main()*/
void insert(int item,int item_priority)
{
struct node *tmp,*p;
tmp=(struct node *)malloc(sizeof(struct node));
if(tmp==NULL)
{
printf("Memory not available\n");
return;
}
tmp->info=item;
tmp->priority=item_priority;
/*Queue is empty or item to be added has priority more than first element*/
if( isEmpty() || item_priority < front->priority )
{
tmp->link=front;
front=tmp;
}
else
{
p = front;
while( p->link!=NULL && p->link->priority<=item_priority )
p=p->link;
tmp->link=p->link;
p->link=tmp;
}
}/*End of insert()*/
int del()
{
struct node *tmp;
int item;
if( isEmpty() )
{
printf("Queue Underflow\n");
exit(1);
}
else
{
tmp=front;
item=tmp->info;
front=front->link;
free(tmp);
}
return item;
}/*End of del()*/
int isEmpty()
{
if( front == NULL )
return 1;
else
return 0;
}/*End of isEmpty()*/
void display()
{
struct node *ptr;
ptr=front;
if( isEmpty() )
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 display() */
1.Insert
2.Delete
3.Display
4.Quit
Enter your choice : 1
Input the item to be added in the queue : 12
Enter its priority : 0
1.Insert
2.Delete
3.Display
4.Quit
Enter your choice : 1
Input the item to be added in the queue : 13
Enter its priority : 1
1.Insert
2.Delete
3.Display
4.Quit
Enter your choice : 1
Input the item to be added in the queue : 15
Enter its priority : 0
1.Insert
2.Delete
3.Display
4.Quit
Enter your choice : 3
Queue is :
Priority Item
0 12
0 15
1 13
1.Insert
2.Delete
3.Display
4.Quit
Enter your choice : 4
Press any key to continue . . .
First understand the algorithm carefully. Then study the program line-by-line and compare it with the output. Finally, review the explanation section to strengthen your logic and programming understanding.
Rewrite the program without looking at the code. Modify values, conditions or logic and run it again. This helps improve confidence and strengthens coding skills much faster.