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
using System;

public class LinkedList
{
    // Head of list
    Node head;

    // Linked list Node
    class Node
    {
        public int data;
        public Node next;
        public Node(int d)
        {
            data = d; next = null;
        }
    }

    // Function to print reverse
    // of linked list
    void printReverse(Node head)
    {
        if (head == null) return;

        // print list of head node
        printReverse(head.next);

        // After everything else is printed
        Console.Write(head.data + " ");
    }

    // Utility Functions

    // Inserts a new Node at front
    // of the list.
    public void push(int new_data)
    {
        /* 1 & 2: Allocate the Node &
                  Put in the data*/
        Node new_node = new Node(new_data);

        // 3. Make next of new Node as head
        new_node.next = head;

        // 4. Move the head to point to
        // new Node
        head = new_node;
    }

    // Driver code
    public static void Main(String []args)
    {
        // Let us create linked list 1->2->3->4
        LinkedList llist = new LinkedList();
        llist.push(4);
        llist.push(3);
        llist.push(2);
        llist.push(1);

        llist.printReverse(llist.head);
    }
}
// This code is contributed by Rajput-Ji

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!