# How to create a pointer to another pointer in a linked list?

In this article we cover how to create a pointer to another pointer in a linked list, it can be singly, doubly, or circularly.

A linked list is a linear data structure, in which the elements are not stored at contiguous memory locations. The elements in a linked list are linked using pointers as shown in the below image:

• In, a singly linked list, each node has a value and a pointer to the next node.
• It is of most common linked list.
• We can go only in one direction, head to tail.

• A Doubly Linked List (DLL) contains an extra pointer, typically called the previous pointer, together with the next pointer and data.
• We can go in both directions, head to tail and tail to head.

• The circular linked list is a linked list where all nodes are connected to form a circle.
• In a circular linked list, the first node and the last node are connected to each other which forms a circle.
• There is no NULL at the end.

### How to create a pointer to another pointer in a linked list?

We can create a pointer to another pointer in a linked list by making a dummy node. Let’s say you want a pointer that should point to the head of the linked list. Usually, we create a dummy pointer with the value -1.

Below is the implementation:

## C++

 `// C++ program to create a pointer to``// another pointer in a linked list` `#include ``using` `namespace` `std;` `class` `Node {` `public``:``    ``int` `data;``    ``Node* next;` `    ``// constructor``    ``Node(``int` `data)``    ``{``        ``this``->data = data;``        ``this``->next = NULL;``    ``}` `    ``// Destructor``    ``~Node()``    ``{``        ``int` `value = ``this``->data;``        ``if` `(``this``->next != NULL) {``            ``delete` `next;``            ``this``->next = NULL;``        ``}``    ``}``};` `// Function to insert value at tail of LL``void` `insertAtTail(Node*& tail, ``int` `d)``{` `    ``// New node create``    ``Node* temp = ``new` `Node(d);``    ``tail->next = temp;``    ``tail = temp;``}` `// Function to print the linked list``void` `print(Node*& head)``{``    ``Node* temp = head;` `    ``while` `(temp != NULL) {``        ``cout << temp->data << ``" "``;``        ``temp = temp->next;``    ``}``    ``cout << endl;``}` `// Function to create a dummy pointer``// and point it to head of linked list``Node* createPointer(Node*& head)``{` `    ``Node* dummy = ``new` `Node(-1);` `    ``dummy->next = head;` `    ``return` `dummy;``}` `// Driver Code``int` `main()``{` `    ``// Created a new node of``    ``// First singly LL``    ``Node* node = ``new` `Node(1);` `    ``// Head pointed to node``    ``Node* head = node;``    ``Node* tail = node;` `    ``insertAtTail(tail, 2);``    ``insertAtTail(tail, 3);``    ``insertAtTail(tail, 4);``    ``insertAtTail(tail, 5);` `    ``cout << ``"Linked List: "` `<< endl;` `    ``print(head);` `    ``Node* pt = createPointer(head);` `    ``cout``        ``<< ``"Dummy pointer pointing to head of Linked List: "``        ``<< endl;` `    ``print(pt);` `    ``return` `0;``}`

## Java

 `// Java program to create a pointer to``// another pointer in a linked list``import` `java.io.*;` `class` `Node {``  ``int` `data;``  ``Node next;``  ` `  ``// constructor``  ``public` `Node(``int` `data)``  ``{``    ``this``.data = data;``    ``this``.next = ``null``;``  ``}``}` `class` `GFG {` `  ``// Function to insert value at tail of LL``  ``static` `Node insertAtTail(Node tail, ``int` `d)``  ``{``    ``// New node create``    ``Node temp = ``new` `Node(d);``    ``tail.next = temp;``    ``tail = temp;``    ``return` `temp;``  ``}` `  ``// Function to print the linked list``  ``static` `void` `printLL(Node head)``  ``{``    ``Node temp = head;``    ``while` `(temp != ``null``) {``      ``System.out.print(temp.data + ``" "``);``      ``temp = temp.next;``    ``}``    ``System.out.println();``  ``}` `  ``// Function to create a dummy pointer``  ``// and point it to head of linked list``  ``static` `Node createPointer(Node head)``  ``{``    ``Node dummy = ``new` `Node(-``1``);``    ``dummy.next = head;``    ``return` `dummy;``  ``}` `  ``public` `static` `void` `main(String[] args)``  ``{``    ``// Created a new node of``    ``// First singly LL``    ``Node node = ``new` `Node(``1``);``    ``// Head pointed to node``    ``Node head = node;``    ``Node tail = node;``    ``tail = insertAtTail(tail, ``2``);``    ``tail = insertAtTail(tail, ``3``);``    ``tail = insertAtTail(tail, ``4``);``    ``tail = insertAtTail(tail, ``5``);``    ``System.out.println(``"Linked List: "``);``    ``printLL(head);``    ``Node pt = createPointer(head);``    ``System.out.println(``      ``"Dummy pointer pointing to head of Linked List: "``);``    ``printLL(pt);``  ``}``}` `// This code is contributed by lokesh.`

## Python3

 `# Python program to create a pointer to``# another pointer in a linked list` `class` `Node:``    ``# constructor``    ``def` `__init__(``self``, data):``        ``self``.data ``=` `data ``        ``self``.``next` `=` `None` `# Function to insert value at tail of LL``def` `insertAtTail(tail, d):``    ``# New node create``    ``temp ``=` `Node(d) ``    ``tail.``next` `=` `temp ``    ``tail ``=` `temp ``    ``return` `temp` `# Function to print the linked list``def` `printLL(head):``    ``temp ``=` `head ``    ``while` `(temp !``=` `None``):``        ``print``(temp.data,end``=``" "``)``        ``temp ``=` `temp.``next``    ``print``()` `# Function to create a dummy pointer``# and point it to head of linked list``def` `createPointer(head):``    ``dummy ``=` `Node(``-``1``) ``    ``dummy.``next` `=` `head ``    ``return` `dummy ` `# Driver Code``# Created a new node of``# First singly LL``node ``=`  `Node(``1``) ``# Head pointed to node``head ``=` `node ``tail ``=` `node ``tail ``=` `insertAtTail(tail, ``2``) ``tail ``=` `insertAtTail(tail, ``3``) ``tail ``=` `insertAtTail(tail, ``4``) ``tail ``=` `insertAtTail(tail, ``5``) ``print``(``"Linked List: "``)``printLL(head) ``pt ``=` `createPointer(head) ``print``(``"Dummy pointer pointing to head of Linked List: "``)``printLL(pt)`

## C#

 `// C# program to create a pointer to``// another pointer in a linked list` `using` `System;` `public` `class` `Node {``    ``public` `int` `data;``    ``public` `Node next;` `    ``// constructor``    ``public` `Node(``int` `data)``    ``{``        ``this``.data = data;``        ``this``.next = ``null``;``    ``}``}` `public` `class` `GFG {` `    ``// Function to insert value at tail of LL``    ``static` `Node insertAtTail(Node tail, ``int` `d)``    ``{``        ``// New node create``        ``Node temp = ``new` `Node(d);``        ``tail.next = temp;``        ``tail = temp;``        ``return` `temp;``    ``}` `    ``// Function to print the linked list``    ``static` `void` `printLL(Node head)``    ``{``        ``Node temp = head;``        ``while` `(temp != ``null``) {``            ``Console.Write(temp.data + ``" "``);``            ``temp = temp.next;``        ``}``        ``Console.WriteLine();``    ``}` `    ``// Function to create a dummy pointer``    ``// and point it to head of linked list``    ``static` `Node createPointer(Node head)``    ``{``        ``Node dummy = ``new` `Node(-1);``        ``dummy.next = head;``        ``return` `dummy;``    ``}` `    ``static` `public` `void` `Main()``    ``{` `        ``// Created a new node of``        ``// First singly LL``        ``Node node = ``new` `Node(1);``        ``// Head pointed to node``        ``Node head = node;``        ``Node tail = node;``        ``tail = insertAtTail(tail, 2);``        ``tail = insertAtTail(tail, 3);``        ``tail = insertAtTail(tail, 4);``        ``tail = insertAtTail(tail, 5);``        ``Console.WriteLine(``"Linked List: "``);``        ``printLL(head);``        ``Node pt = createPointer(head);``        ``Console.WriteLine(``            ``"Dummy pointer pointing to head of Linked List: "``);``        ``printLL(pt);``    ``}``}` `// This code is contributed by lokeshmvs21.`

## Javascript

 `class Node {``  ``constructor(data) {``    ``this``.data = data;``    ``this``.next = ``null``;``  ``}``}` `function` `insertAtTail(tail, d) {``    ``const temp = ``new` `Node(d);``    ``tail.tail.next = temp;``    ``tail.tail = temp;``}` `function` `print(head) {``    ``let temp = head;``    ``while` `(temp != ``null``) {``        ``process.stdout.write(temp.data + ``' '``);``        ``temp = temp.next;``    ``}``    ``console.log();``}` `function` `createPointer(head) {``    ``const dummy = ``new` `Node(-1);``    ``dummy.next = head;``    ``return` `dummy;``}` `const node = ``new` `Node(1);``const head = node;``const tail = { tail: node };` `insertAtTail(tail, 2);``insertAtTail(tail, 3);``insertAtTail(tail, 4);``insertAtTail(tail, 5);` `console.log(``"Linked List:"``);``print(head);` `const pt = createPointer(head);` `console.log(``"Dummy pointer pointing to head of Linked List:"``);``print(pt);`

Output
```Linked List:
1 2 3 4 5
-1 1 2 3 4 5
```

Time Complexity: O(1)
Auxiliary Space: O(1)

If you want to point to any other Node except the head then you have to first traverse to the node in the linked list. Then you can point the dummy pointer to it.

• Time for traversing: O(N)
• Time for creating the dummy node: O(1)
• Time to point it to the given node: O(1)

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