/*********************************************************************/
/*PROGRAM TO INSERT A NEW NODE IN THE BEGINNING OF LINEAR LINKED LIST*/
/*********************************************************************/

						
#include<stdio.h>
#include<conio.h>
#include<malloc.h>
#include<process.h>
#include<ctype.h>
struct linear_list
{
	int info;
	struct linear_list *next;
}*start,*newnode,*ptr;

void menu();
void create();
void display_traverse();
int list_empty();
int count();

void insert_beg(int);

void main()
{
	clrscr();
	menu();
}

void menu()
{
	int choice,loc,loc1,item,num,var;
	printf("MENU");
	printf("\n1. Create");
	printf("\n2. Display/Traverse");
	printf("\n3. Insertion in the beginning");
	printf("\n4.Exit");
	printf("\nEnter your choice: ");
	scanf("%d",&choice);
	switch(choice)
	{
		case 1:
			create();
			clrscr();
			printf("The created linked list is:\n");
			display_traverse();
			getch();
			clrscr();
			menu();
			break;
		case 2:
			clrscr();
			if(list_empty()==1)
			{
				printf("The linked list is:\n");
				display_traverse();
			}
			getch();
			clrscr();
			menu();
			break;
		case 3:
			clrscr();
			printf("\nEnter the item tobe inserted: ");
			scanf("%d",&item);
			insert_beg(item);
			clrscr();
			printf("\nAfter insertion in the beginning the linked list is:\n");
			display_traverse();
			getch();
			clrscr();
			menu();
			break;

		case 4:
			exit(1);
		default:
			clrscr();
			printf("Your choice is wrong\n\n");
			menu();
	}
}

void create()
{
	int item;
	char ch;
	clrscr();
	newnode=(struct linear_list*)malloc(sizeof(struct linear_list));
	start=newnode;
	do
	{
		printf("\nEnter data: ");
		scanf("%d",&item);
		newnode->info=item;
		printf("\nDo you want to create another node:(y/n)");
		fflush(stdin);
		scanf("%c",&ch);
		if(tolower(ch)=='y')
		{
			newnode->next=(struct linear_list*)malloc(sizeof(struct linear_list));
			newnode=newnode->next;
		}
		else
		{
			newnode->next=NULL;
		}
	}while(tolower(ch)!='n');
}

void display_traverse()
{
	int i;
	ptr=start;
	i=1;
	while(ptr!=NULL)
	{
		printf("\nNode %d : %d",i,ptr->info);
		ptr=ptr->next;
		i++;
	}
}

int list_empty()
{
	if(start==NULL)
	{
		printf("\nLinked List is empty");
		return(0);
	}
	else
	{
		return(1);
	}
}

void insert_beg(int item)
{
	newnode=(struct linear_list*)malloc(sizeof(struct linear_list));
	newnode->info=item;
	if(start==NULL)
	{
		start=newnode;
		newnode->next=NULL;
	}
	else
	{
		newnode->next=start;
		start=newnode;
	}
}