/*Write a program to create a singly linked list.
1->Creation.
2->insertion.
3->deletion.*/
#include<stdio.h>
#include<stdlib.h>
void creation();
void display();
void insert_end();
void insert_beginning();
void insert_middle();
void deletion();
struct link_list
{
    int data;
    struct link_list *next;
}*start=NULL;
typedef struct link_list node;
node *current,*nnew;
void main()
{
    int a;
    char ch;
    clrscr();
    creation();
    do
    {
        printf("\nenter your choice\n1->display\n2->insert at end\n3->insert at beginning\n4->insert b/w two nodes\n5->deletion\n");
        scanf("%d",&a);
        switch(a)
        {
            case 1:
            display();
            break;
            case 2:
            {
                insert_end();
            }
            break;
            case 3:
            {
                insert_beginning();
            }
            break;
            case 4:
            {
                insert_middle();
            }
            break;
            case 5:
            {
                deletion();
            }
            break;
            default:
            printf("wrong choice");
        }
        printf("\npress any key to continue and press n to quit");
        scanf("%s",&ch);
    }while(ch!='n');
}

void creation()
{
    int i=0,k;
    printf("how many nodes you want to create ");
    scanf("%d",&i);
    while(i!=0)
    {
        nnew=(node*)malloc(sizeof(node));
        nnew->next=NULL;
        if(start==NULL)
        {
            printf("enter any integer data ");
            scanf("%d",&k);
            nnew->data=k;
            start=nnew;
            current=start;
        }
        else
        {
            printf("enter any integer data ");
            scanf("%d",&k);
            nnew->data=k;
            current->next=nnew;
            current=nnew;
        }
        i--;
    }
}

void display()
{
    int i=1;
    current=start;
    while(current!=NULL)
    {
        printf("%d:: %d\n",i ,current->data);
        current=current->next;
        i++;
    }
    getch();
}

void insert_end()
{
    current=start;
    while(current->next!=NULL)
    {
        current=current->next;
        if(current->next==NULL)
        {
            nnew=(node*)malloc(sizeof(node));
            nnew->next=NULL;
            printf("enter the deta for this node ");
            scanf("%d",&nnew->data);
            current->next=nnew;
            current=nnew;
            printf("node inserted successfully");
        }
    }
}

void insert_beginning()
{
    nnew=(node*)malloc(sizeof(node));
    nnew->next=NULL;
    printf("enter the deta for this node ");
    scanf("%d",&nnew->data);
    nnew->next=start;
    start=nnew;
    printf("node inserted successfully\n");
}
void insert_middle()
{
    int a,i,pos,b;
    current=start;
    nnew=(node*)malloc(sizeof(node));
    nnew->next=NULL;
    printf("enter the deta for this node ");
    scanf("%d",&nnew->data);
    printf("enter the serial number of node accept first and the last node ");
    scanf("%d",&pos);
    printf("enter 1 to insert after the selected node and 2 for before ");
    scanf("%d",&a);
    if(a==1)
    {
        current=start;
        for(i=1;i<pos;i++)
        {
            current=current->next;
        }
        nnew->next=current->next;
        current->next=nnew;
    }
    else if(a==2)
    {
        current=start;
        for(i=1;i<pos-1;i++)
        {
            current=current->next;
        }
        nnew->next=current->next;
        current->next=nnew;
    }
    else
    {
        printf("wrong choice");
    }
}

void deletion()
{
    int y,i;
    current=start;
    printf("enter the serial number of node you want to delete ");
    scanf("%d",&y);
    if(y==1)
    {
        start=start->next;
    }
    for(i=1;i<y-1;i++)
    {
        current=current->next;
    }
    if(current->next->next==NULL)
    {
        current->next=NULL;
    }
    else
    {
        current->next=current->next->next;
    }
    printf("node is deleted");
}