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++
// 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 beginning, // 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
// 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 beginning, // 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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Python3
# Python3 Program to print doubly # linked list in reverse order import math # Doubly linked list node class Node: def __init__(self, data): self.data = data self.next = None # Function to print nodes of Doubly # Linked List in reverse order def reversePrint(head_ref): tail = head_ref # Traversing till tail of the linked list while (tail.next != None): tail = tail.next # Traversing linked list from tail # and pring the node.data while (tail != head_ref): print(tail.data, end = " ") tail = tail.prev print(tail.data) # UTILITY FUNCTIONS # Function to insert a node at the # beginging of the Doubly Linked List def push(head_ref, new_data): # allocate node new_node = Node(new_data) # put in the data new_node.data = new_data # since we are adding at the beginning, # prev is always None new_node.prev = None # link the old list off the new node new_node.next = head_ref # change prev of head node to new node if (head_ref != None): head_ref.prev = new_node # move the head to po to the new node head_ref = new_node return head_ref # Driver Code if __name__=='__main__': # Start with the empty list head = None # 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) print("Linked List elements in reverse order : ") reversePrint(head) # This code is contributed by Srathore |
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C#
// C# Program to print doubly // linked list in reverse order using System; class Sol { // Doubly linked list node public class Node { public int data; public Node next; public 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) { Console.Write( tail.data + " "); tail = tail.prev; } Console.WriteLine( 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 beginning, // 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); Console.Write( "Linked List elements in reverse order : " ); reversePrint(head); } } // This code contributed by Rajput-Ji |
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Output:
Linked List elements in reverse order : 2 4 8 10
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