Program to reverse a linked list using Stack

18 May, 2022
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:  
Traverse the list and push all of its nodes onto a stack.Traverse the list from the head node again and pop a value from the stack top and connect them in reverse order.
Traverse the list and push all of its nodes onto a stack.
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++
Java
Python3
C#
Javascript
// C/C++ program to reverse linked list// using stack  #include <bits/stdc++.h>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 listNode *reverseList(Node* head){    // Stack to store elements of list    stack<Node *> 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 listvoid printList(Node* head){    while (head) {        cout << head->data << " ";        head = head->next;    }}  // Driver Codeint 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 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<Node > stk = new Stack<Node> ();       // 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 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# 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<Node > stk = new Stack<Node> ();       // 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
<script>        // JavaScript program to reverse linked list      // using stack      /* Link list node */      class Node {        constructor() {          this.data = 0;          this.next = null;        }      }      var 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. */      function push(new_data) {        var new_node = new Node();          new_node.data = new_data;        new_node.next = head;        head = new_node;      }        // Function to reverse linked list      function reverseList(head) {        // Stack to store elements of list        var stk = [];          // Push the elements of list to stack        var ptr = head;        while (ptr.next != null) {          stk.push(ptr);          ptr = ptr.next;        }          // Pop from stack and replace        // current nodes value'        head = ptr;        while (stk.length != 0) {          ptr.next = stk[stk.length - 1];          ptr = ptr.next;          stk.pop();        }        ptr.next = null;          return head;      }        // Function to print the Linked list      function printList(head) {        while (head != null) {          document.write(head.data + " ");          head = head.next;        }      }        // Driver Code      /* 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);        </script>
5 4 3 2 1
 
Time Complexity : O(n), as we are traversing over the linked list of size N using a while loop.
Auxiliary Space: O(N), as we are using stack of size N in worst case which is extra space.We can reverse a linked list with O(1) auxiliary space. See more methods to reverse a linked list. 
prerna saini
rituraj_jain
VishalBachchas
Rajput-Ji
rdtank
rohitsingh07052
Python DSA-exercises
Python LinkedList-exercises
Python-Data-Structures
Reverse
Linked List
Stack
Linked List
Stack
Reverse
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