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

struct node
{
    char info[20];
    struct node *ptr;
}*front,*rear,*temp,*front1;


void enq(char data[]);
void deq();
void empty();
void display();
void create();
void queuesize();

int count = 0;

void main()
{
    int ch;
    char no[20];
    create();

    while (1)
    {

        printf("\n 1 - Enque");
        printf("\n 2 - Deque");
        printf("\n 3 - Empty");
        printf("\n 4 - Exit");
        printf("\n 5 - Display");
        printf("\n 6 - Queue size");

        printf("\n Enter choice : ");
        scanf("%d", &ch);
        switch (ch)
        {
            case 1:
            printf("Please enter the Vehical ID : ");
            scanf("%s", &no);
            enq(no);
            break;
            case 2:
            deq();
            break;
            case 3:
            empty();
            break;
            case 4:
            exit(0);
            case 5:
            display();
            break;
            case 6:
            queuesize();
            break;
            default:
            printf("Wrong choice, Please enter correct choice ");
            break;
        }
    }
}

/* Create an empty queue */
void create()
{
    front = rear = NULL;
}

/* Returns queue size */
void queuesize()
{
    printf("\n Queue size : %d", count);
}

/* Enqueing the queue */
void enq(char data[])
{
    if (rear == NULL)
    {
        rear = (struct node *)malloc(1*sizeof(struct node));
        rear->ptr = NULL;
        strcpy(rear->info, data);
        front = rear;
    }
    else
    {
        temp=(struct node *)malloc(1*sizeof(struct node));
        rear->ptr = temp;
        strcpy(temp->info, data);
        temp->ptr = NULL;

        rear = temp;
    }
    count++;
}

/* Displaying the queue elements */
void display()
{
    front1 = front;

    if ((front1 == NULL) && (rear == NULL))
    {
        printf("Queue is empty");
        return;
    }
    while (front1 != rear)
    {
        printf("%s ", front1->info);
        front1 = front1->ptr;
    }

    if (front1 == rear)
        printf("%s", front1->info);
}

/* Dequeing the queue */
void deq()
{
front1 = front;

if (front1 == NULL)
{
    printf("\n Error: Trying to display elements from empty queue");
    return;
}
else if (front1->ptr != NULL)
{
    front1 = front1->ptr;
    printf("\n Dequed value : %s", front->info);
    free(front);
    front = front1;
}
else
{
    printf("\n Dequed value : %s", front->info);
    free(front);
    front = NULL;
    rear = NULL;
}
count--;
}


/* Display if queue is empty or not */
void empty()
{
    if ((front == NULL) && (rear == NULL))
    printf("\n Queue empty");
    else
    printf("Queue not empty");
}