Code:
#include stdio.h
#include stdlib.h
#define MAX 5
void insert_by_priority(int);
void delete_by_priority(int);
void create();
void check(int);
void display_pqueue();
int pri_que[MAX];
int front, rear;
void main()
{
int n, ch;
printf("\n1 - Insert an element into queue");
printf("\n2 - Delete an element from queue");
printf("\n3 - Display queue elements");
printf("\n4 - Exit");
create();
while (1)
{
printf("\nEnter your choice : ");
scanf("%d", &ch);
switch (ch)
{
case 1:
printf("\nEnter value to be inserted : ");
scanf("%d",&n);
insert_by_priority(n);
break;
case 2:
printf("\nEnter value to delete : ");
scanf("%d",&n);
delete_by_priority(n);
break;
case 3:
display_pqueue();
break;
case 4:
exit(0);
default:
printf("\nChoice is incorrect, Enter a correct choice");
}
}
}
/* Function to create an empty priority queue */
void create()
{
front = rear = -1;
}
/* Function to insert value into priority queue */
void insert_by_priority(int data)
{
if (rear >= MAX - 1)
{
printf("\nQueue overflow no more elements can be inserted");
return;
}
if ((front == -1) && (rear == -1))
{
front++;
rear++;
pri_que[rear] = data;
return;
}
else
check(data);
rear++;
}
/* Function to check priority and place element */
void check(int data)
{
int i,j;
for (i = 0; i <= rear; i++)
{
if (data >= pri_que[i])
{
for (j = rear + 1; j > i; j--)
{
pri_que[j] = pri_que[j - 1];
}
pri_que[i] = data;
return;
}
}
pri_que[i] = data;
}
/* Function to delete an element from queue */
void delete_by_priority(int data)
{
int i;
if ((front==-1) && (rear==-1))
{
printf("\nQueue is empty no elements to delete");
return;
}
for (i = 0; i <= rear; i++)
{
if (data == pri_que[i])
{
for (; i < rear; i++)
{
pri_que[i] = pri_que[i + 1];
}
pri_que[i] = -99;
rear--;
if (rear == -1)
front = -1;
return;
}
}
printf("\n%d not found in queue to delete", data);
}
/* Function to display queue elements */
void display_pqueue()
{
if ((front == -1) && (rear == -1))
{
printf("\nQueue is empty");
return;
}
for (; front <= rear; front++)
{
printf(" %d ", pri_que[front]);
}
front = 0;
}
Output:
1 - Insert an element into queue
2 - Delete an element from queue
3 - Display queue elements
4 - Exit
Enter your choice : 1
Enter value to be inserted : 20
Enter your choice : 1
Enter value to be inserted : 45
Enter your choice : 1
Enter value to be inserted : 89
Enter your choice : 3
89 45 20
Enter your choice : 1
Enter value to be inserted : 56
Enter your choice : 3
89 56 45 20
Enter your choice : 2
Enter value to delete : 45
Enter your choice : 3
89 56 20
Enter your choice : 4
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