Question

This is a c programming problem.

Would you please help me to write this problem???

I really appreciate it if you add comments for explanation step by step.

Thank you.

Reverse a Doubly linked list using recursion: Given a doubly linked list. Reverse it using recursion. Original Doubly linked list: next pointer - DDHIHI Null prev painter Reversed Doubly linked list: next pointer Start Pointer Null prev pointer Include: a) A struct for a node of the doubly linked list. b) A function to get a new node. c) A function to insert a node at the beginning of the Doubly Linked List. d) A function to delete the last node from the doubly linked list. e) A function to print nodes in a given doubly linked list. f) A function to reverse a doubly linked list, using recursion.

Answer 1

Code:

#include <stdio.h>
#include <stdlib.h>

struct Node
{
   int value;
   struct Node* prev;
   struct Node* next;
};

struct Node* start = NULL;

struct Node* getNewNode(int val)
{
   struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
   newNode->value = val;
   newNode->prev = NULL;
   newNode->next = NULL;
   return newNode;
}

void insertAtBeginnning(struct Node* newNode)
{
   if (start == NULL)
   {
       start = newNode;
   }
   else
   {
       start->prev = newNode;
       newNode->next = start;
       start = newNode;
   }
}

void deleteLastNode()
{
   struct Node* temp = start;
   struct Node* prevNode = NULL;
   while (temp->next != NULL)
   {
       prevNode = temp;
       temp = temp->next;
   }

   prevNode->next = NULL;

   free(temp);
}

void print()
{
   printf("\n");
   struct Node* temp = start;
   while (temp != NULL)
   {
       if (temp->next == NULL)
           printf("%d", temp->value);
       else
           printf("%d --> ", temp->value);
       temp = temp->next;
   }
}

void reverse(struct Node* aNode)
{
   if (aNode->next == NULL)
   {
       //When it reaches the last node assign the start pointer as the last node
       start = aNode;
       //Swap the prev pointer and the next pointer of the last node
       struct Node* temp = aNode->prev;
       aNode->prev = aNode->next;
       aNode->next = temp;
       return;
   }

   //Call recursively till it reaches the last node
   reverse(aNode->next);

   //Swap the prev pointer and the next pointer of all the nodes during stack unwinding.
   struct Node* temp = aNode->prev;
   aNode->prev = aNode->next;
   aNode->next = temp;
}

int main()
{
   insertAtBeginnning(getNewNode(2));
   insertAtBeginnning(getNewNode(4));
   insertAtBeginnning(getNewNode(8));
   insertAtBeginnning(getNewNode(10));

   printf("\n Before reversing \n");

   print();

   printf("\n After reversing \n");

   reverse(start);

   print();

   return 0;
}

OUTPUT:

Before reversing 2 10 --> 8 --> 4 --> After reversing 2 --> 4 --> 8 --> 10