#include <stdio.h>

#include <stdlib.h>

  

// A linked list node

struct Node

{

  int data;

  struct Node *next;

};

  

/* Given a reference (pointer to pointer) to the head of a list and 

   an int, inserts a new node on the front of the list. */

void push(struct Node** head_ref, int new_data)

{

    /* 1. allocate node */

    struct Node* new_node = (struct Node*) malloc(sizeof(struct Node));

  

    /* 2. put in the data  */

    new_node->data  = new_data;

  

    /* 3. Make next of new node as head */

    new_node->next = (*head_ref);

  

    /* 4. move the head to point to the new node */

    (*head_ref)    = new_node;

}

  

/* Given a node prev_node, insert a new node after the given 

   prev_node */

void insertAfter(struct Node* prev_node, int new_data)

{

    /*1. check if the given prev_node is NULL */

    if (prev_node == NULL)

    {

      printf("the given previous node cannot be NULL");

      return;

    }

  

    /* 2. allocate new node */

    struct Node* new_node =(struct Node*) malloc(sizeof(struct Node));

  

    /* 3. put in the data  */

    new_node->data  = new_data;

  

    /* 4. Make next of new node as next of prev_node */

    new_node->next = prev_node->next;

  

    /* 5. move the next of prev_node as new_node */

    prev_node->next = new_node;

}

  

/* Given a reference (pointer to pointer) to the head

   of a list and an int, appends a new node at the end  */

void append(struct Node** head_ref, int new_data)

{

    /* 1. allocate node */

    struct Node* new_node = (struct Node*) malloc(sizeof(struct Node));

  

    struct Node *last = *head_ref;  /* used in step 5*/

  

    /* 2. put in the data  */

    new_node->data  = new_data;

  

    /* 3. This new node is going to be the last node, so make next of

          it as NULL*/

    new_node->next = NULL;

  

    /* 4. If the Linked List is empty, then make the new node as head */

    if (*head_ref == NULL)

    {

       *head_ref = new_node;

       return;

    }

  

    /* 5. Else traverse till the last node */

    while (last->next != NULL)

        last = last->next;

  

    /* 6. Change the next of last node */

    last->next = new_node;

    return;

}

  

// This function prints contents of linked list starting from head

void printList(struct Node *node)

{

  while (node != NULL)

  {

     printf(" %d ", node->data);

     node = node->next;

  }

}

  

/* Driver program to test above functions*/

int main()

{

  /* Start with the empty list */

  struct Node* head = NULL;

  

  // Insert 6.  So linked list becomes 6->NULL

  append(&head, 6);

  

  // Insert 7 at the beginning. So linked list becomes 7->6->NULL

  push(&head, 7);

  

  // Insert 1 at the beginning. So linked list becomes 1->7->6->NULL

  push(&head, 1);

  

  // Insert 4 at the end. So linked list becomes 1->7->6->4->NULL

  append(&head, 4);

  

  // Insert 8, after 7. So linked list becomes 1->7->8->6->4->NULL

  insertAfter(head->next, 8);

  

  printf("\n Created Linked list is: ");

  printList(head);

  

  return 0;

}