QUEUS USING SINGLE LINKED LIST

#include <stdio.h>

#include <stdlib.h>

#include<malloc.h>

 struct node

{

    int info;

    struct node *ptr;

}*front,*rear,*temp,*front1;

void enq(int data);

void deq();

void empty();

void display();

int count = 0;

void main()

{

    int no, ch, e;

    printf("\n 1 - Enque");

    printf("\n 2 - Deque");

    printf("\n 3 - Empty");

    printf("\n 4 - Exit");

    printf("\n 5 - Display");

    while (1)

    {

        printf("\n Enter choice : ");

        scanf("%d", &ch);

        switch (ch)

        {

        case 1:

            printf("Enter data : ");

            scanf("%d", &no);

            enq(no);

            break;

        case 2:

            deq();

            break;

        case 3:

            empty();

            break;

        case 4:

            exit(0);

        case 5:

            display();

            break;

        default:

            printf("Wrong choice, Please enter correct choice  ");

            break;

        }

    }

}

void enq(int data)

{

    if (rear == NULL)

    {

        rear = (struct node *)malloc(sizeof(struct node));

        rear->ptr = NULL;

        rear->info = data;

        front = rear;

    }

    else

    {

        temp=(struct node *)malloc(sizeof(struct node));

        rear->ptr = temp;

        temp->info = data;

        temp->ptr = NULL;

        rear = temp;

    }

    count++;

}

void display()

{

    front1 = front;

    if ((front1 == NULL) && (rear == NULL))

    {

        printf("Queue is empty");

        return;

    }

    while (front1 != rear)

    {

        printf("%d ", front1->info);

        front1 = front1->ptr;

    }

    if (front1 == rear)

        printf("%d", front1->info);

}

void deq()

{

    front1 = front;

    if (front1 == NULL)

    {

        printf("\n Error: Trying to delete elements from empty queue");

        return;

    }

    else

        if (front1->ptr != NULL)

        {

            front1 = front1->ptr;

            printf("\n Dequed value : %d", front->info);

            free(front);

            front = front1;

        }

        else

        {

            printf("\n Dequed value : %d", front->info);

            free(front);

            front = NULL;

            rear = NULL;

        }

        count--;

}

void empty()

{

     if ((front == NULL) && (rear == NULL))

        printf("\n Queue empty");

    else

       printf("Queue not empty");

}