Reverse_a_linked_list.java

// { Driver Code Starts
import java.util.*;
import java.io.*;

class Node{
    int data;
    Node next;
    
    Node(int x){
        data = x;
        next = null;
    }
    
}
class GFG{
    static void printList(Node node) 
    { 
        while (node != null) 
        { 
            System.out.print(node.data + " "); 
            node = node.next; 
        } 
        System.out.println(); 
    }
    public static void main(String args[]) throws IOException { 
        
        Scanner sc = new Scanner(System.in);
        int t = sc.nextInt();
        
        while(t > 0){
        
            int n = sc.nextInt();
        
            Node head = new Node(sc.nextInt());
            Node tail = head;
        
            for(int i=0; i<n-1; i++)
            {
                tail.next = new Node(sc.nextInt());
                tail = tail.next;
            }
        
            ReverseLL g = new ReverseLL();
            head = g.reverseList(head);
            printList(head); 
            t--;
        }
    } 
} 

class ReverseLL{
    Node reverseList(Node head){
        Node curr = head, next = null, prev = null;
        
        while( curr != null ){
            next = curr.next;
            curr.next = prev;
            prev = curr;
            curr = next;
        }
        
        return prev;
    }

    Node reverseListR(Node head){
        if( head == null || head.next == null ){
            return head;
        }

        Node rest = reverseListR(head.next);
        head.next.next = head;

        head.next = null;

        return rest;
    }
}