Invertir una lista doblemente enlazada usando recursividad

Dada una lista doblemente enlazada. Invertirlo usando recursividad.

Original Doubly linked list 

Reversed Doubly linked list 

Hemos discutido 
la solución iterativa para revertir una lista doblemente enlazada

Algoritmo:

1. Si la lista está vacía, devuelve 
2. Cabeza inversa intercambiando cabeza->anterior y cabeza->siguiente 
3. Si prev = NULL significa que la lista está completamente invertida. De lo contrario, revertir (cabeza-> anterior) 

Implementación:

// C++ implementation to reverse a doubly
// linked list using recursion
#include <bits/stdc++.h>
using namespace std;
 
// a node of the doubly linked list
struct Node {
    int data;
    Node *next, *prev;
};
 
// function to get a new node
Node* getNode(int data)
{
    // allocate space
    Node* new_node = new Node;
    new_node->data = data;
    new_node->next = new_node->prev = NULL;
    return new_node;
}
 
// function to insert a node at the beginning
// of the Doubly Linked List
void push(Node** head_ref, Node* new_node)
{
    // 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;
}
 
// function to reverse a doubly linked list
Node* Reverse(Node* node)
{
    // If empty list, return
    if (!node)
        return NULL;
 
    // Otherwise, swap the next and prev
    Node* temp = node->next;
    node->next = node->prev;
    node->prev = temp;
 
    // If the prev is now NULL, the list
    // has been fully reversed
    if (!node->prev)
        return node;
 
    // Otherwise, keep going
    return Reverse(node->prev);
}
 
// Function to print nodes in a given doubly
// linked list
void printList(Node* head)
{
    while (head != NULL) {
        cout << head->data << " ";
        head = head->next;
    }
}
 
// Driver program to test above
int main()
{
    // Start with the empty list
    Node* head = NULL;
 
    // Create doubly linked: 10<->8<->4<->2 */
    push(&head, getNode(2));
    push(&head, getNode(4));
    push(&head, getNode(8));
    push(&head, getNode(10));
    cout << "Original list: ";
    printList(head);
 
    // Reverse doubly linked list
    head = Reverse(head);
    cout << "\nReversed list: ";
    printList(head);
    return 0;
}

// Java implementation to reverse a doubly
// linked list using recursion
class GFG
{
     
// a node of the doubly linked list
static class Node
{
    int data;
    Node next, prev;
};
 
// function to get a new node
static Node getNode(int data)
{
    // allocate space
    Node new_node = new Node();
    new_node.data = data;
    new_node.next = new_node.prev = null;
    return new_node;
}
 
// function to insert a node at the beginning
// of the Doubly Linked List
static Node push(Node head_ref, Node new_node)
{
    // 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;
}
 
// function to reverse a doubly linked list
static Node Reverse(Node node)
{
    // If empty list, return
    if (node == null)
        return null;
 
    // Otherwise, swap the next and prev
    Node temp = node.next;
    node.next = node.prev;
    node.prev = temp;
 
    // If the prev is now null, the list
    // has been fully reversed
    if (node.prev == null)
        return node;
 
    // Otherwise, keep going
    return Reverse(node.prev);
}
 
// Function to print nodes in a given doubly
// 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;
 
    // Create doubly linked: 10<.8<.4<.2 /
    head = push(head, getNode(2));
    head = push(head, getNode(4));
    head = push(head, getNode(8));
    head = push(head, getNode(10));
    System.out.print( "Original list: ");
    printList(head);
 
    // Reverse doubly linked list
    head = Reverse(head);
    System.out.print("\nReversed list: ");
    printList(head);
}
}
 
// This code is contributed by Arnab Kundu

# Python3 implementation to reverse a doubly
# linked list using recursion
import math
 
# a node of the doubly linked list
class Node:
    def __init__(self, data):
        self.data = data
        self.next = None
 
# function to get a new node
def getNode(data):
     
    # allocate space
    new_node = Node(data)
    new_node.data = data
    new_node.next = new_node.prev = None
    return new_node
 
# function to insert a node at the beginning
# of the Doubly Linked List
def push(head_ref, new_node):
     
    # 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 point to the new node
    head_ref = new_node
    return head_ref
 
# function to reverse a doubly linked list
def Reverse(node):
     
    # If empty list, return
    if not node:
        return None
 
    # Otherwise, swap the next and prev
    temp = node.next
    node.next = node.prev
    node.prev = temp
 
    # If the prev is now None, the list
    # has been fully reversed
    if not node.prev:
        return node
 
    # Otherwise, keep going
    return Reverse(node.prev)
 
# Function to print nodes in a given doubly
# linked list
def printList(head):
    while (head != None) :
        print(head.data, end = " ")
        head = head.next
     
# Driver Code
if __name__=='__main__':
     
    # Start with the empty list
    head = None
 
    # Create doubly linked: 10<.8<.4<.2 */
    head = push(head, getNode(2));
    head = push(head, getNode(4));
    head = push(head, getNode(8));
    head = push(head, getNode(10));
    print("Original list: ", end = "")
    printList(head)
     
    # Reverse doubly linked list
    head = Reverse(head)
    print("\nReversed list: ", end = "")
    printList(head)
     
# This code is contributed by Srathore

// C# implementation to reverse a doubly
using System;
 
// linked list using recursion
class GFG
{
     
// a node of the doubly linked list
public class Node
{
    public int data;
    public Node next, prev;
};
 
// function to get a new node
static Node getNode(int data)
{
    // allocate space
    Node new_node = new Node();
    new_node.data = data;
    new_node.next = new_node.prev = null;
    return new_node;
}
 
// function to insert a node at the beginning
// of the Doubly Linked List
static Node push(Node head_ref, Node new_node)
{
    // 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;
}
 
// function to reverse a doubly linked list
static Node Reverse(Node node)
{
    // If empty list, return
    if (node == null)
        return null;
 
    // Otherwise, swap the next and prev
    Node temp = node.next;
    node.next = node.prev;
    node.prev = temp;
 
    // If the prev is now null, the list
    // has been fully reversed
    if (node.prev == null)
        return node;
 
    // Otherwise, keep going
    return Reverse(node.prev);
}
 
// Function to print nodes in a given doubly
// linked list
static void printList(Node head)
{
    while (head != null)
    {
        Console.Write( head.data + " ");
        head = head.next;
    }
}
 
// Driver code
public static void Main(String []argsS)
{
    // Start with the empty list
    Node head = null;
 
    // Create doubly linked: 10<.8<.4<.2 /
    head = push(head, getNode(2));
    head = push(head, getNode(4));
    head = push(head, getNode(8));
    head = push(head, getNode(10));
    Console.Write( "Original list: ");
    printList(head);
 
    // Reverse doubly linked list
    head = Reverse(head);
    Console.Write("\nReversed list: ");
    printList(head);
}
}
 
// This code is contributed by Arnab Kundu

<script>
// javascript implementation to reverse a doubly
// linked list using recursion    
// a node of the doubly linked list
class Node {
    constructor(val) {
        this.data = val;
        this.prev = null;
        this.next = null;
    }
}
 
    // function to get a new node
    function getNode(data) {
        // allocate space
var new_node = new Node();
        new_node.data = data;
        new_node.next = new_node.prev = null;
        return new_node;
    }
 
    // function to insert a node at the beginning
    // of the Doubly Linked List
    function push(head_ref,  new_node) {
        // 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;
    }
 
    // function to reverse a doubly linked list
    function Reverse(node) {
        // If empty list, return
        if (node == null)
            return null;
 
        // Otherwise, swap the next and prev
var temp = node.next;
        node.next = node.prev;
        node.prev = temp;
 
        // If the prev is now null, the list
        // has been fully reversed
        if (node.prev == null)
            return node;
 
        // Otherwise, keep going
        return Reverse(node.prev);
    }
 
    // Function to print nodes in a given doubly
    // linked list
    function printList(head) {
        while (head != null) {
            document.write(head.data + " ");
            head = head.next;
        }
    }
 
    // Driver code
     
        // Start with the empty list
var head = null;
 
        // Create doubly linked: 10<.8<.4<.2 /
        head = push(head, getNode(2));
        head = push(head, getNode(4));
        head = push(head, getNode(8));
        head = push(head, getNode(10));
        document.write("Original list: ");
        printList(head);
 
        // Reverse doubly linked list
        head = Reverse(head);
        document.write("<br/>Reversed list: ");
        printList(head);
 
// This code contributed by umadevi9616
</script>

Original list: 10 8 4 2 
Reversed list: 2 4 8 10