C Program For Printing Reverse Of A Linked List Without Actually Reversing

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.
Note that the question is only about printing the reverse. To reverse the list itself see this
Difficulty Level: Rookie 

Algorithm: 

printReverse(head)
  1. call print reverse for head->next
  2. print head->data

Implementation:

C

// C program to print reverse
// of a linked list
#include<stdio.h>
#include<stdlib.h>

// Link list node
struct Node
{
    int data;
    struct Node* next;
};

// Function to reverse the linked list
void printReverse(struct Node* head)
{
    // Base case
    if (head == NULL)
       return;

    // Print the list after head node
    printReverse(head->next);

    // After everything else is printed,
    // print head
    printf("%d  ", head->data);
}

// UTILITY FUNCTIONS
/* Push a node to linked list.
   Note that this function
   changes the head */
void push(struct Node** head_ref,
          char 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 of the
    // new node
    new_node->next = (*head_ref);

    // Move the head to point to the
    // new node
    (*head_ref)    = new_node;
}

// Driver code
int main()
{
    // Create linked list 1->2->3->4
    struct Node* head = NULL;
    push(&head, 4);
    push(&head, 3);
    push(&head, 2);
    push(&head, 1);

    printReverse(head);
    return 0;
}

Output:

4 3 2 1

Time Complexity: O(n)

Space Complexity: O(n) for call stack since using recursion

Please refer complete article on Print reverse of a Linked List without actually reversing for more details!