program for Implementation of a Queues with example

Program

A complete C program to implement a queue by using an array is shown here:

#include <stdio.h>
#define MAX 10 /* The maximum size of the queue */
#include <stdlib.h>

void insert(int queue[], int *rear, int value)
{
   if(*rear < MAX-1)
   {
      *rear= *rear +1;
      queue[*rear] = value;
   }
   else
   {
      printf("The queue is full can not insert a value\n");
      exit(0);
   }
}

void delete(int queue[], int *front, int rear, int * value)
{
   if(*front == rear)
   {
      printf("The queue is empty can not delete a value\n");
      exit(0);
   }
   *front = *front + 1;
   *value = queue[*front];
}

void main()
{
   int queue[MAX];
   int front,rear;
   int n,value;
   front=rear=(-1);
   do
   {
      do
      {
            printf("Enter the element to be inserted\n");
         scanf("%d",&value);
         insert(queue,&rear,value);
         printf("Enter 1 to continue\n");
            scanf("%d",&n);
      } while(n == 1);

      printf("Enter 1 to delete an element\n");
      scanf("%d",&n);
      while( n == 1)
      {
            delete(queue,&front,rear,&value);
         printf("The value deleted is %d\n",value);
            printf("Enter 1 to delete an element\n");
         scanf("%d",&n);
      }
      printf("Enter 1 to continue\n");
      scanf("%d",&n);
   } while(n == 1);
}

Example

Input and Output

Enter the element to be inserted

10

Enter 1 to continue

1

Enter the element to be inserted

20

Enter 1 to continue

1

Enter the element to be inserted

30

Enter 1 to continue

0

Enter 1 to delete an element

1

The value deleted is 10
Enter 1 to delete an element

1

The value deleted is 20
Enter 1 to delete an element

0

Enter 1 to continue

1

Enter the element to be inserted

40

Enter 1 to continue

1

Enter the element to be inserted

50

Enter 1 to continue

0

Enter 1 to delete an element

1

The value deleted is 30
Enter 1 to delete an element

1

The value deleted is 40
Enter 1 to delete an element

0

Enter 1 to continue

0