I have to accept user input, a string, into a doubly linked list and print the output reversed and forward. My professor gave us the following program and told us to modify it. However, I cannot figure it out.
/* Program to reverse a doubly linked list */
#include <stdio.h>
#include <stdlib.h>
/* a node of the doubly linked list */
struct node
{
int data;
struct node *next;
struct node *prev;
};
/* Function to reverse a Doubly Linked List */
void reverse(struct node **head_ref)
{
struct node *temp = NULL;
struct node *current = *head_ref;
/* swap next and prev for all nodes of
doubly linked list */
while (current != NULL)
{
temp = current->prev;
current->prev = current->next;
current->next = temp;
current = current->prev;
}
/* Before changing head, check for the cases like empty
list and list with only one node */
if(temp != NULL )
*head_ref = temp->prev;
}
/* 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 begining,
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 print nodes in a given doubly linked list
This function is same as printList() of singly linked lsit */
void printList(struct node *node)
{
while(node!=NULL)
{
printf("%d ", node->data);
node = node->next;
}
}
/* Drier program to test above functions*/
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, 1);
push(&head, 2);
push(&head, 10);
printf("\n Original Linked list ");
printList(head);
/* Reverse doubly linked list */
reverse(&head);
printf("\n Reversed Linked list ");
printList(head);
getchar();
}
I tried changing the main function to this:
int main()
{
/* Start with the empty list */
struct node* head = NULL;
char str[400];
scanf("%s", head);
push(&head);
printf("\n Original Linked list ");
printList(head);
/* Reverse doubly linked list */
reverse(&head);
printf("\n Reversed Linked list ");
printList(head);
getchar();
}
but did not work. I would appreciate any help, hints, clues. Thanks!
