QUESTION

Given a linked list, print reverse of it using a recursive function. For example, if the given linked list is 1->2->3->4, then output should be 4->3->2->1.

“TESTCASE_1”: “5\n5 4 4 3 2\n###—###SEPERATOR—###—\n2 3 4 4 5”, “TESTCASE_2”: “6 \n1 1 1 5 6 9\n###—###SEPERATOR—###—\n9 6 5 1 1 1”, “TESTCASE_3”: “4\n2 1 4 3\n###—###SEPERATOR—###—\n3 4 1 2”, “TESTCASE_4”: “7\n1 2 6 3 9 4 5\n###—###SEPERATOR—###—\n5 4 9 3 6 2 1”, “TESTCASE_5”: “0\n###—###SEPERATOR—###—\n0

ANSWER

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


struct Node
{
    int data;
    struct Node* next;
};


static void reverse(struct Node** head_ref)
{
    struct Node* prev   = NULL;
    struct Node* current = *head_ref;
    struct Node* next = NULL;
    while (current != NULL)
    {
        next  = current->next;  
        current->next = prev;   
        prev = current;
        current = next;
    }
    *head_ref = prev;
}

/* Function to push a node */
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;
               
    /* link the old list off the new node */
    new_node->next = (*head_ref);    
       
    /* move the head to point to the new node */
    (*head_ref)    = new_node;
}

/* Function to print linked list */
void printList(struct Node *head)
{
    struct Node *temp = head;
    while(temp != NULL)
    {
        printf("%d ", temp->data);    
        temp = temp->next;  
    }
}    

/* Driver program to test above function*/
int main()
{
    /* Start with the empty list */
    struct Node* head = NULL;
  int n,i;
  scanf("%d",&n);
  int arr[n];
  for(i=0;i<n;i++)
    scanf("%d",&arr[i]);
  for(i=n-1;i>=0;i--)
     push(&head, arr[i]);
     
     
     reverse(&head);                      
     
     printList(head);    
     return 0;
}