C Program For Reversing A Doubly Linked List
Given a Doubly Linked List, the task is to reverse the given Doubly Linked List.
See below diagrams for example.
(a) Original Doubly Linked List
(b) Reversed Doubly Linked List
Here is a simple method for reversing a Doubly Linked List. All we need to do is swap prev and next pointers for all nodes, change prev of the head (or start) and change the head pointer in the end.
C
#include <stdio.h>
#include <stdlib.h>
struct Node
{
int data;
struct Node *next;
struct Node *prev;
};
void reverse( struct Node **head_ref)
{
struct Node *temp = NULL;
struct Node *current = *head_ref;
while (current != NULL)
{
temp = current->prev;
current->prev = current->next;
current->next = temp;
current = current->prev;
}
if (temp != NULL )
*head_ref = temp->prev;
}
void push( struct Node** head_ref,
int new_data)
{
struct Node* new_node =
( struct Node*) malloc ( sizeof ( struct Node));
new_node->data = new_data;
new_node->prev = NULL;
new_node->next = (*head_ref);
if ((*head_ref) != NULL)
(*head_ref)->prev = new_node ;
(*head_ref) = new_node;
}
void printList( struct Node *node)
{
while (node!=NULL)
{
printf ( "%d " , node->data);
node = node->next;
}
}
int main()
{
struct Node* head = NULL;
push(&head, 2);
push(&head, 4);
push(&head, 8);
push(&head, 10);
printf (
"Original Linked list " );
printList(head);
reverse(&head);
printf (
"Reversed Linked list " );
printList(head);
getchar ();
}
|
Output:
Original linked list
10 8 4 2
The reversed Linked List is
2 4 8 10
Time Complexity: O(N), where N denotes the number of nodes in the doubly linked list.
Auxiliary Space: O(1)
We can also swap data instead of pointers to reverse the Doubly Linked List. Method used for reversing array can be used to swap data. Swapping data can be costly compared to pointers if the size of the data item(s) is more.
Please write comments if you find any of the above codes/algorithms incorrect, or find better ways to solve the same problem.
Please refer complete article on Reverse a Doubly Linked List for more details!
Last Updated :
03 Apr, 2023
Like Article
Save Article
Share your thoughts in the comments
Please Login to comment...