Circular_Queue.c

#include <stdio.h>
#include <stdlib.h>

struct circularQueue
{
     int size;
     int f;
     int r;
     int *arr;
};

int isEmpty(struct circularQueue *q)
{
     if (q->r == q->f)
     {
          return 1;
     }
     return 0;
}

int isFull(struct circularQueue *q)
{
     if ((q->r + 1) % q->size == q->f)
     {
          return 1;
     }
     return 0;
}

void enqueue(struct circularQueue *q, int val)
{
     if (isFull(q))
     {
          printf("This Queue is full\n");
     }
     else
     {
          q->r = (q->r + 1) % q->size;
          q->arr[q->r] = val;
          printf("Enqued element: %d\n", val);
     }
}

int dequeue(struct circularQueue *q)
{
     int a = -1;
     if (isEmpty(q))
     {
          printf("This Queue is empty\n");
     }
     else
     {
          q->f = (q->f + 1) % q->size;
          a = q->arr[q->f];
     }
     return a;
}

int main()
{
     struct circularQueue q;
     q.size = 4;
     q.f = q.r = 0;
     q.arr = (int *)malloc(q.size * sizeof(int));

     // Enqueue few elements
     enqueue(&q, 12);
     enqueue(&q, 15);
     enqueue(&q, 1);
     printf("Dequeuing element %d\n", dequeue(&q));
     printf("Dequeuing element %d\n", dequeue(&q));
     printf("Dequeuing element %d\n", dequeue(&q));
     enqueue(&q, 45);
     enqueue(&q, 45);
     enqueue(&q, 45);

     if (isEmpty(&q))
     {
          printf("Queue is empty\n");
     }
     if (isFull(&q))
     {
          printf("Queue is full\n");
     }

     return 0;
}