linked_list.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;
 
    /* 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(Node *node)
{
    while (node != NULL)
    {
        cout<<" "<<node->data;
        node = node->next;
    }
}
 
// Driver code
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);
     
    // 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);
     
    cout << "Created Linked list is: ";
    printList(head);
     
    return 0;
}