linklist.cpp

#include <bits/stdc++.h>
using namespace std;
 
// A linked list node
class Node
{
    public:
    int data;
    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(Node** head_ref, int new_data)
{
   
    // 1. allocate node
    Node* new_node = new 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(Node* prev_node, int new_data)
{
    // 1. check if the given prev_node
    // is NULL
    if (prev_node == NULL)
    {
        cout<<"The given previous node cannot be NULL";
        return;
    }
 
    // 2. allocate new node
    Node* new_node = new 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(Node** head_ref, int new_data)
{
   
    // 1. allocate node
    Node* new_node = new Node();
 
    //used in step 5
    Node *last = *head_ref;
 
    // 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;
 
  
    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;
}
 

void printList(Node *node)
{
    while (node != NULL)
    {
        cout<<" "<<node->data;
        node = node->next;
    }
}
 

int main()
{
   
    // Start with the empty list
    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);
     
  
    push(&head, 1);
     
 
    append(&head, 4);
     
  
    insertAfter(head->next, 8);
     
    cout<<"Created Linked list is: ";
    printList(head);
     
    return 0;
}