Katbin

/* Linked list again! Because i'm addicted to it!! */
/* This time just the creation and printing it */

/* Importing necessary libraries */
#include 
#include 


/* Create a Node structure */
struct node
{
    int data;
    struct node *next;
};


struct node *head;


/* Function prototype(s) */ 
void printNodes(struct node *n);
void freeNodes(struct node *n);
void insertNode(struct node *n, int pos);
int listLength(struct node *n);


/* Driver function */
int main()
{
    int no_of_nodes, insert_choice;
    struct node *temp;

    /* Asking to enter the number of nodes */
    printf("Enter the number of nodes : ");
    scanf("%d", &no_of_nodes);

    /* Create HEAD node if atleast 1 Node, if not exit indicating a failure. */
    if (no_of_nodes >= 1 )
    {
        head = malloc(sizeof(struct node));
        printf("Enter Head Node's Data : ");
        scanf("%d", &(head -> data));
        head -> next = NULL;
        temp = head;
    }
    else{
        exit(-1);
    }

    /* Creating the nodes after HEAD */
    for (int i=0; i < no_of_nodes - 1; i++)
    {
        struct node *n = malloc(sizeof(struct node));
        temp -> next = n;
        printf("Enter Node %d data : ", i+1);
        scanf("%d", &(n -> data));

        temp = n;
    }
    temp -> next = NULL;    /* There's no next node to the last node in a single linked list, so giving it NULL. */
    
    printNodes(head);
    printf("Wanna insert a Node ?\n1 : YES\n2 : NO\n(Press 1 or 2) : ");
    switch (scanf("%d", &insert_choice))
    {
        case 1:
                int pos;
                printNodes(head);
                printf("Enter the position [Note: Starting Position is 0] : ");
                scanf("%d", &pos);
                insertNode(head, pos);
                break;
    
        case 2:
                break;
        default:
            printf("Choose either 0 or 1.");
            break;
    }

    printNodes(head);
    freeNodes(head);
    return 0;
}   

/* This function traverses through each Node and prints the Data resides in it. */
void printNodes(struct node *n)
{
    //printf("%d", n -> data);
    while(n != NULL)
    {   
        if (n -> next != NULL)
            printf("%d%s", n -> data, " -> ");
        else
            printf("%d%s", n -> data, " -> NULL\n");
        n = n->next;
    }
}

/* This function will release the memory allocated to the node structure manually */
/* It traverses through each node and releases their memory after taking note of the pointer to the next node. */
void freeNodes(struct node *n)
{
    struct node *temp;

    while(n != NULL)
    {
        temp = n;
        n = n -> next;
        free(temp);
    }
}


/* Inserting a Node at Nth position */
void insertNode (struct node *head, int pos)
{
    int len = listLength(head);
    struct node *n;

    if (pos > len || pos < 0)
    {
        printf("Position you have chosen is out of bounds of the length of the Linked List.\n");
    }

    n = malloc(sizeof(struct node));
    printf("Enter the Node data : ");
    scanf("%d", &(n -> data));

    if (pos == 0)
    {
        printf("Pos was 0, so HEAD\n");
        n -> next = head;
        head = n;
        printNodes(head);
    }   
    else if ( pos == (len - 1) )
    {
        printf("Pos was last, so TAIL\n");

        while ( head != NULL )
        {
            head = head -> next;
        }
        head -> next = n;
        n -> next = NULL;
    }
    else
    {
        printf("Pos was middle, so owo\n");

        for (int i = 0; i < pos - 1; i++)
        {
            head = head -> next;
        }
        n -> next = head -> next;
        head -> next = n;
    }

    
}


int listLength(struct node *n)
{
    int count = 0;
    while (n != NULL)
    {
        count++;
        n = n -> next;
    }

    return count;
}