ADT_Linklist_node_insert.c

// author: jaydattpatel
#include<stdio.h>
#include<stdlib.h>

struct Node
    {
        int data;
        struct Node * next;
    };

void Traversal(struct Node *ptr)
    {
        while (ptr != NULL)
        {
            printf("Element: %d\n", ptr->data);
            ptr = ptr->next;
        }
    }

// Case 1
struct Node * insertAtFirst(struct Node *head, int data)
    {
        struct Node * ptr = (struct Node *) malloc(sizeof(struct Node));
        ptr->data = data;
        ptr->next = head;
        return ptr; 
    }

// Case 2
struct Node * insertAtIndex(struct Node *head, int data, int index)
    {
        struct Node * ptr = (struct Node *) malloc(sizeof(struct Node));
        struct Node * p = head;
        int i = 0;

        while (i!=index-1)
        {
            p = p->next;
            i++;
        }
        ptr->data = data;
        ptr->next = p->next;
        p->next = ptr;
        return head;
    }

// Case 3
struct Node * insertAtEnd(struct Node *head, int data)
    {
        struct Node * ptr = (struct Node *) malloc(sizeof(struct Node));
        ptr->data = data;
        struct Node * p = head;

        while(p->next!=NULL){
            p = p->next;
        }
        p->next = ptr;
        ptr->next = NULL;
        return head;
    }

// Case 4
struct Node * insertAfterNode(struct Node *head, struct Node *prevNode, int data)
    {
        struct Node * ptr = (struct Node *) malloc(sizeof(struct Node));
        ptr->data = data;
        ptr->next = prevNode->next;
        prevNode->next = ptr;
        return head;
    }


int main()
{
    struct Node *head;
    struct Node *second;
    struct Node *third;
    struct Node *fourth;

    // Allocate memory for nodes in the linked list in Heap
    head = (struct Node *)malloc(sizeof(struct Node));
    second = (struct Node *)malloc(sizeof(struct Node));
    third = (struct Node *)malloc(sizeof(struct Node));
    fourth = (struct Node *)malloc(sizeof(struct Node));

    // Link first and second nodes
    head->data = 7;
    head->next = second;

    // Link second and third nodes
    second->data = 11;
    second->next = third;

    // Link third and fourth nodes
    third->data = 41;
    third->next = fourth;

    // Terminate the list at the third node
    fourth->data = 66;
    fourth->next = NULL;

    printf("Linked list before insertion\n");
    Traversal(head);
    head = insertAtFirst(head, 23);
    head = insertAtIndex(head, 56, 2);
    head = insertAtEnd(head, 96);
    head = insertAfterNode(head, third, 45);
    printf("\nLinked list after insertion\n");
    Traversal(head);

    return 0;
}