Print Doubly Linked list in Reverse Order

Given a doubly linked list of positive integers. The task is to print the given doubly linked list data in reverse order.

Examples:

Input: List = 1 <=> 2 <=>  3 <=>  4 <=>  5
Output: 5  4  3  2  1

Input: 10 <=> 20 <=> 30 <=> 40
Output: 40  30  20  10


Approach:

  • Take a pointer to point to head of the doubly linked list.
  • Now, start traversing through the linked list till the end.
  • After reaching last node, start traversing in backward direction and simultaneously print the node->data.

Below is the implementation of the above approach:

C++

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// C++ Program to print doubly 
// linked list in reverse order 
#include <bits/stdc++.h>
using namespace std;
  
// Doubly linked list node
struct Node {
    int data;
    struct Node* next;
    struct Node* prev;
};
  
// Function to print nodes of Doubly 
// Linked List in reverse order 
void reversePrint(struct Node** head_ref)
{
    struct Node* tail = *head_ref;
  
    // Traversing till tail of the linked list
    while (tail->next != NULL) {
        tail = tail->next;
    }
  
    // Traversing linked list from tail
    // and printing the node->data
    while (tail != *head_ref) {
        cout << tail->data << " ";
        tail = tail->prev;
    }
    cout << tail->data << endl;
}
  
/* UTILITY FUNCTIONS */
// Function to insert a node at the 
// beginging of the Doubly Linked List 
void push(struct Node** head_ref, int new_data)
{
    // allocate node 
    struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
  
    // put in the data 
    new_node->data = new_data;
  
    // since we are adding at the begining, 
    // prev is always NULL 
    new_node->prev = NULL;
  
    // link the old list off the new node 
    new_node->next = (*head_ref);
  
    // change prev of head node to new node 
    if ((*head_ref) != NULL)
        (*head_ref)->prev = new_node;
  
    // move the head to point to the new node 
    (*head_ref) = new_node;
}
  
// Driver Code
int main()
{
    // Start with the empty list 
    struct Node* head = NULL;
  
    // Let us create a sorted linked list
    // to test the functions 
    // Created linked list will be 10->8->4->2 
    push(&head, 2);
    push(&head, 4);
    push(&head, 8);
    push(&head, 10);
  
    cout << "Linked List elements in reverse order : " << endl;
  
    reversePrint(&head);
  
    return 0;
}

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Java

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// Java Program to print doubly 
// linked list in reverse order 
class Sol
{
  
// Doubly linked list node 
static class Node
    int data; 
    Node next; 
    Node prev; 
}; 
  
// Function to print nodes of Doubly 
// Linked List in reverse order 
static void reversePrint( Node head_ref) 
    Node tail = head_ref; 
  
    // Traversing till tail of the linked list 
    while (tail.next != null)
    
        tail = tail.next; 
    
  
    // Traversing linked list from tail 
    // and printing the node.data 
    while (tail != head_ref)
    
        System.out.print( tail.data + " "); 
        tail = tail.prev; 
    
    System.out.println( tail.data ); 
  
// UTILITY FUNCTIONS /
// Function to insert a node at the 
// beginging of the Doubly Linked List 
static Node push( Node head_ref, int new_data) 
    // allocate node 
    Node new_node = new Node(); 
  
    // put in the data 
    new_node.data = new_data; 
  
    // since we are adding at the begining, 
    // prev is always null 
    new_node.prev = null
  
    // link the old list off the new node 
    new_node.next = (head_ref); 
  
    // change prev of head node to new node 
    if ((head_ref) != null
        (head_ref).prev = new_node; 
  
    // move the head to point to the new node 
    (head_ref) = new_node; 
    return head_ref;
  
// Driver Code 
public static void main(String args[])
    // Start with the empty list 
    Node head = null
  
    // Let us create a sorted linked list 
    // to test the functions 
    // Created linked list will be 10.8.4.2 
    head = push(head, 2); 
    head = push(head, 4); 
    head = push(head, 8); 
    head = push(head, 10); 
  
    System.out.print( "Linked List elements in reverse order : " ); 
  
    reversePrint(head); 
}
  
// This code is contributed by Arnab Kundu 

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Output:

Linked List elements in reverse order : 
2 4 8 10


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