Circular Queue Operations Using Counter

/*Circular queue operations using counter, 
Circular queue programs, Insert in circular queue,delete in circular queue*/
#include <stdio.h>

#define max 5
struct queue {
    int items[max];
    int front, rear, counter;
};

void display(struct queue *pq) {
    int i;
    if (pq->counter == 0) {
        printf("Queue underflow!!\n");
    } else {
        printf("The queue items are:\n");
        for (i = 0; i < pq->counter; i++) {
            printf("%5d", pq->items[(i + pq->front + 1) % max]);
        }
    }
}

void insrt(struct queue *pq) {
    int val;
    if (pq->counter == max) {
        printf("Queue overflow!\n");
    } else {
        printf("Enter the data to insert: ");
        scanf("%d", &val);
        pq->rear = (pq->rear + 1) % max;
        pq->items[pq->rear] = val;
        pq->counter++;
    }
}

void delt(struct queue *pq) {
    int x;
    if (pq->counter == 0) {
        printf("Queue underflow!\n");
    } else {
        pq->front = (pq->front + 1) % max;
        x = pq->items[pq->front];
        printf("The deleted data of queue is: %d\n", x);
        pq->counter--;
    }
}
void main() {
    struct queue *q;
    int x;
    q->front = max - 1;
    q->rear = max - 1;
    q->counter = 0;
    while (1) {
        printf("\nMENU");

        printf("\n1.Enqueue\n2.Dequeue\n3.Display all items\n4.Exit\n");

        printf("\nEnter your choice: ");
        scanf("%d", &x);

        switch (x) {
            case 1:
                insrt(q);
                break;
            case 2:
                delt(q);
                break;
            case 3:
                display(q);
                break;
            case 4:
                exit(1);
            default:
                printf("\nInvalid Choice!\n");
        }
    }
}




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