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  1. /* Program to reverse a doubly linked list */
  2. #include <stdio.h>
  3. #include <stdlib.h>
  4.  
  5. /* a node of the doubly linked list */
  6. struct node
  7. {
  8.   int data;
  9.   struct node *next;
  10.   struct node *prev;    
  11. };
  12.  
  13. /* Function to reverse a Doubly Linked List */
  14. void reverse(struct node **head_ref)
  15. {
  16.      struct node *temp = NULL;  
  17.      struct node *current = *head_ref;
  18.  
  19.      /* swap next and prev for all nodes of 
  20.        doubly linked list */
  21.      while (current !=  NULL)
  22.      {
  23.        temp = current->prev;
  24.        current->prev = current->next;
  25.        current->next = temp;              
  26.        current = current->prev;
  27.      }      
  28.  
  29.      /* Before changing head, check for the cases like empty 
  30.         list and list with only one node */
  31.      if(temp != NULL )
  32.         *head_ref = temp->prev;
  33. }     
  34.  
  35.  
  36.  
  37. /* UTILITY FUNCTIONS */
  38. /* Function to insert a node at the beginging of the Doubly Linked List */
  39. void push(struct node** head_ref, int new_data)
  40. {
  41.     /* allocate node */
  42.     struct node* new_node =
  43.             (struct node*) malloc(sizeof(struct node));
  44.  
  45.     /* put in the data  */
  46.     new_node->data  = new_data;
  47.  
  48.     /* since we are adding at the begining, 
  49.       prev is always NULL */
  50.     new_node->prev = NULL;
  51.  
  52.     /* link the old list off the new node */
  53.     new_node->next = (*head_ref);    
  54.  
  55.     /* change prev of head node to new node */
  56.     if((*head_ref) !=  NULL)
  57.       (*head_ref)->prev = new_node ;    
  58.  
  59.     /* move the head to point to the new node */
  60.     (*head_ref)    = new_node;
  61. }
  62.  
  63. /* Function to print nodes in a given doubly linked list 
  64.    This function is same as printList() of singly linked lsit */
  65. void printList(struct node *node)
  66. {
  67.   while(node!=NULL)
  68.   {
  69.    printf("%d ", node->data);
  70.    node = node->next;
  71.   }
  72. } 
  73.  
  74. /* Drier program to test above functions*/
  75. int main()
  76. {
  77.   /* Start with the empty list */
  78.   struct node* head = NULL;
  79.  
  80.   /* Let us create a sorted linked list to test the functions
  81.    Created linked list will be 10->8->4->2 */
  82.   push(&head, 2);
  83.   push(&head, 4);
  84.   push(&head, 8);
  85.   push(&head, 10);
  86.  
  87.   printf("\n Original Linked list ");
  88.   printList(head);
  89.  
  90.   /* Reverse doubly linked list */
  91.   reverse(&head);
  92.  
  93.   printf("\n Reversed Linked list ");
  94.   printList(head);           
  95.  
  96.   getchar();
  97. }
Success #stdin #stdout 0s 3472KB
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stdin
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Standard input is empty
stdout
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 Original Linked list 10 8 4 2 
 Reversed Linked list 2 4 8 10
https://ideone.com/WSQ0iV
language:
C++14 (clang 8.0)
created:
7 years ago
visibility:
public

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