Queue using linked list cprogram

Aim:Implementation of queue using linked list in C program

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Program:

#include<stdio.h>

#include<conio.h>

#include<alloc.h>

void enque(int);

void deque();

void display();

struct queue

{

int data;

struct queue *next;

};

typedef struct queue node;

node *rear,*front,*new,*dfront;

void main()

{

int ch,item;

clrscr();

front=rear=NULL;

while(1)

{

printf("1.enque\t2.deque\t3.display\t4.exit\n");

printf("enter your choice");

scanf("%d",&ch);

switch(ch)

{

case 1:

printf("enter the element to insert");

scanf("%d",&item);

enque(item);

break;

case 2:

deque();

break;

case 3:

printf("elements in queue are: ");

display();

break;

default :

exit(0);

}

}

}

void enque(int item)

{

if(rear==NULL)

{

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

rear->data=item;

rear->next=NULL;

front=rear;

}

else

{

new=(node *)malloc(sizeof(node));

new->data=item;

new->next=NULL;

rear->next=new;

rear=new;

}

}

void deque()

{

if(front==NULL)

printf("underflow\n");

else

{

printf("element deleted is %d\n",front->data);

if(front==rear)

front=rear=NULL;

else

front=front->next;

}

}

void display()

{       dfront=front;

while(dfront!=NULL)/*dfront means duplicate front*/

{

printf("%d ",dfront->data);

dfront=dfront->next;

}

printf("\n");

}

Output: