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# Program to reverse a linked list using Stack

• Difficulty Level : Medium
• Last Updated : 21 Jun, 2021

Given a linked list. The task is to reverse the order of the elements of the Linked List using an auxiliary Stack.
Examples:

```Input : List = 3 -> 2 -> 1
Output : 1 -> 2 -> 3

Input : 9 -> 7 -> 4 -> 2
Output : 2 -> 4 -> 7 -> 9 ```

Algorithm

1. Traverse the list and push all of its nodes onto a stack.
2. Traverse the list from the head node again and pop a value from the stack top and connect them in reverse order.

Below is the implementation of the above approach:

## C++

 `// C/C++ program to reverse linked list``// using stack` `#include ``using` `namespace` `std;` `/* Link list node */``struct` `Node {``    ``int` `data;``    ``struct` `Node* next;``};` `/* Given a reference (pointer to pointer) to``   ``the head of a list and an int, push a new``   ``node on the front of the list. */``void` `push(``struct` `Node** head_ref, ``int` `new_data)``{``    ``struct` `Node* new_node = ``new` `Node;` `    ``new_node->data = new_data;``    ``new_node->next = (*head_ref);``    ``(*head_ref) = new_node;``}` `// Function to reverse linked list``Node *reverseList(Node* head)``{``    ``// Stack to store elements of list``    ``stack stk;` `    ``// Push the elements of list to stack``    ``Node* ptr = head;``    ``while` `(ptr->next != NULL) {``        ``stk.push(ptr);``        ``ptr = ptr->next;``    ``}` `    ``// Pop from stack and replace``    ``// current nodes value'``    ``head = ptr;``    ``while` `(!stk.empty()) {``        ``ptr->next = stk.top();` `        ``ptr = ptr->next;``        ``stk.pop();``    ``}``    ` `    ``ptr->next = NULL;``    ` `    ``return` `head;``}` `// Function to print the Linked list``void` `printList(Node* head)``{``    ``while` `(head) {``        ``cout << head->data << ``" "``;``        ``head = head->next;``    ``}``}` `// Driver Code``int` `main()``{``    ``/* Start with the empty list */``    ``struct` `Node* head = NULL;` `    ``/* Use push() to construct below list``    ``1->2->3->4->5 */``    ``push(&head, 5);``    ``push(&head, 4);``    ``push(&head, 3);``    ``push(&head, 2);``    ``push(&head, 1);` `    ``head = reverseList(head);` `    ``printList(head);` `    ``return` `0;``}`

## Java

 `// Java program to reverse linked list``// using stack``import` `java.util.*;``class` `GfG``{` `/* Link list node */``static` `class` `Node``{``    ``int` `data;``    ``Node next;``}``static` `Node head = ``null``;` `/* Given a reference (pointer to pointer) to``the head of a list and an int, push a new``node on the front of the list. */``static` `void` `push( ``int` `new_data)``{``    ``Node new_node = ``new` `Node();` `    ``new_node.data = new_data;``    ``new_node.next = (head);``    ``(head) = new_node;``}` `// Function to reverse linked list``static` `Node reverseList(Node head)``{``    ``// Stack to store elements of list``    ``Stack stk = ``new` `Stack ();` `    ``// Push the elements of list to stack``    ``Node ptr = head;``    ``while` `(ptr.next != ``null``)``    ``{``        ``stk.push(ptr);``        ``ptr = ptr.next;``    ``}` `    ``// Pop from stack and replace``    ``// current nodes value'``    ``head = ptr;``    ``while` `(!stk.isEmpty())``    ``{``        ``ptr.next = stk.peek();``        ``ptr = ptr.next;``        ``stk.pop();``    ``}``    ``ptr.next = ``null``;``    ` `    ``return` `head;``}` `// Function to print the Linked list``static` `void` `printList(Node head)``{``    ``while` `(head != ``null``)``    ``{``        ``System.out.print(head.data + ``" "``);``        ``head = head.next;``    ``}``}` `// Driver Code``public` `static` `void` `main(String[] args)``{``    ``/* Start with the empty list */``    ``//Node head = null;` `    ``/* Use push() to construct below list``    ``1->2->3->4->5 */``    ``push( ``5``);``    ``push( ``4``);``    ``push( ``3``);``    ``push( ``2``);``    ``push( ``1``);` `    ``head = reverseList(head);` `    ``printList(head);``}``}` `// This code is contributed by Prerna Saini.`

## Python3

 `# Python3 program to reverse a linked``# list using stack` `# Link list node``class` `Node:``    ` `    ``def` `__init__(``self``, data, ``next``):``        ``self``.data ``=` `data``        ``self``.``next` `=` `next` `class` `LinkedList:``    ` `    ``def` `__init__(``self``):``        ``self``.head ``=` `None``        ` `    ``# Function to push a new Node in``    ``# the linked list``    ``def` `push(``self``, new_data):``    ` `        ``new_node ``=` `Node(new_data, ``self``.head)``        ``self``.head ``=` `new_node``    ` `    ``# Function to reverse linked list``    ``def` `reverseList(``self``):``    ` `        ``# Stack to store elements of list``        ``stk ``=` `[]``    ` `        ``# Push the elements of list to stack``        ``ptr ``=` `self``.head``        ``while` `ptr.``next` `!``=` `None``:``            ``stk.append(ptr)``            ``ptr ``=` `ptr.``next``    ` `        ``# Pop from stack and replace``        ``# current nodes value'``        ``self``.head ``=` `ptr``        ``while` `len``(stk) !``=` `0``:``            ``ptr.``next` `=` `stk.pop()``            ``ptr ``=` `ptr.``next``        ` `        ``ptr.``next` `=` `None``    ` `    ``# Function to print the Linked list``    ``def` `printList(``self``):``        ` `        ``curr ``=` `self``.head``        ``while` `curr:``            ``print``(curr.data, end ``=` `" "``)``            ``curr ``=` `curr.``next` `# Driver Code``if` `__name__ ``=``=` `"__main__"``:` `    ``# Start with the empty list``    ``linkedList ``=` `LinkedList()` `    ``# Use push() to construct below list``    ``# 1.2.3.4.5``    ``linkedList.push(``5``)``    ``linkedList.push(``4``)``    ``linkedList.push(``3``)``    ``linkedList.push(``2``)``    ``linkedList.push(``1``)` `    ``linkedList.reverseList()` `    ``linkedList.printList()` `# This code is contributed by Rituraj Jain`

## C#

 `// C# program to reverse linked list``// using stack``using` `System;``using` `System.Collections.Generic;` `class` `GfG``{` `/* Link list node */``public` `class` `Node``{``    ``public` `int` `data;``    ``public` `Node next;``}``static` `Node head = ``null``;` `/* Given a reference (pointer to pointer) to``the head of a list and an int, push a new``node on the front of the list. */``static` `void` `push( ``int` `new_data)``{``    ``Node new_node = ``new` `Node();` `    ``new_node.data = new_data;``    ``new_node.next = (head);``    ``(head) = new_node;``}` `// Function to reverse linked list``static` `Node reverseList(Node head)``{``    ``// Stack to store elements of list``    ``Stack stk = ``new` `Stack ();` `    ``// Push the elements of list to stack``    ``Node ptr = head;``    ``while` `(ptr.next != ``null``)``    ``{``        ``stk.Push(ptr);``        ``ptr = ptr.next;``    ``}` `    ``// Pop from stack and replace``    ``// current nodes value'``    ``head = ptr;``    ``while` `(stk.Count != 0)``    ``{``        ``ptr.next = stk.Peek();``        ``ptr = ptr.next;``        ``stk.Pop();``    ``}``    ``ptr.next = ``null``;``    ` `    ``return` `head;``}` `// Function to print the Linked list``static` `void` `printList(Node head)``{``    ``while` `(head != ``null``)``    ``{``        ``Console.Write(head.data + ``" "``);``        ``head = head.next;``    ``}``}` `// Driver Code``public` `static` `void` `Main(String[] args)``{``    ``/* Start with the empty list */``    ``//Node head = null;` `    ``/* Use push() to construct below list``    ``1->2->3->4->5 */``    ``push( 5);``    ``push( 4);``    ``push( 3);``    ``push( 2);``    ``push( 1);` `    ``head = reverseList(head);` `    ``printList(head);``}``}` `// This code contributed by Rajput-Ji`

## Javascript

 ``
Output:

`5 4 3 2 1`

Time Complexity : O(n)
We can reverse a linked list with O(1) auxiliary space. See more methods to reverse a linked list.

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