Queue implementation through linked list

Originally Posted by rahul.mca2001

linked list implementation is compile time or run time

void qdelete(node **front,node **rear)
{
    node *delnode;      /* Node to be deleted */
    if((*front)==NULL && (*rear)==NULL)
        printf("\nQueue is empty to delete any element\n");
    else
    {
        delnode=*front;
        (*front)=(*front)->next;
        (*front)->rear = NULL;
        free(delnode);
    }
}

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

typedef struct node
{
	int data;
	struct node *next;
};

void init(node *front, node *rear, int value)
{
	node *newnode;
	newnode=(node *)malloc(sizeof(node));
	newnode->data=value;
	front->next=newnode;
	rear->next=newnode;
	newnode->next=NULL;
}

void ins(node *rear, int value)
{
	node *newnode;
	newnode=(node *)malloc(sizeof(node));
	newnode->data=value;
	newnode->next=NULL;
	(rear->next)->next=newnode;
   rear->next=newnode;
}

void del(node *front, node *rear)
{
	node *del;
	if(front->next==NULL && rear->next==NULL)
		printf("\nList is empty....nothing to delete\n");
	else if(front->next==rear->next && (rear->next)->next==NULL)
		printf("\nYou cannot delete the last node\n");
	else
	{
		del=front->next;
		front->next=(front->next)->next;
		free(del);
		}
}

void display(node *front, node *rear)
{
	node *move=front->next;
	if(front->next==NULL && rear->next==NULL)
		printf("\nList is empty....nothing to display\n");
	else
	{
		while(move->next!=NULL)
		{
			printf("\n%5d\n", move->data);
			move=move->next;
		}
		printf("\n%5d\n", move->data);
	}
}

void main()
{
	node *front, *rear;
	int i,n;
	static int k=0;
	char ch;
	front=(node *)malloc(sizeof(node));
	rear=(node *)malloc(sizeof(node));
	front->next=NULL;
	rear->next=NULL;
	printf("\nWelcome\n");
	do
	{
		again:
		printf("\nEnter 1 for INITIALISE, 2 for INSERT, 3 for DELETE, 4 for DISPLAY\t");
		scanf("%d", &i);
		if(k==0 && i!=1)
		{
			printf("\nYou must initialise first\n");
			goto again;
		}
		else if(k==0 && i==1)
			k=1;
		else if(k==1 && i==1)
		{
			printf("\nInitialisation can occur only once....now you can push values\n");
			goto again;
		}
		else
			goto done;

		done:
		switch(i)
		{
			case 1:
			{
				printf("\nEnter the value you want to initialise=");
				scanf("%d", &n);
				init(front,rear,n);
				break;
			}

			case 2:
			{
				printf("\nEnter the value you want to insert=");
				scanf("%d", &n);
				ins(rear,n);
				break;
			}

			case 3:
			{
				del(front,rear);
				break;
			}

			case 4:
			{
				display(front,rear);
				break;
			}

			default:
			{
				printf("\nERROR...please re-enter the code\n");
				break;
			}
		}
		printf("\nDo you wish to continue?[y/n]\t");
		ch=getche();
		printf("\n");
	}while(ch=='y'||ch=='Y');
	printf("\nThank you....press any key to exit\n");
	getch();
}