Reverse a Linked List.

class ListNode{
    int value;
    ListNode next;
    ListNode(int val){
        value = val;
        next = null;
    }
}

public class Solution{

    static ListNode makeList(int size){
        ListNode head = new ListNode(1);
        ListNode prev = head;

        for(int i=2;i<=size;++i){
            ListNode current = new ListNode(i);
            prev.next = current;
            prev = current;
        }

        return head;
    }

    static ListNode reverseList(ListNode head){
        ListNode prev = null,current=head,next_node = null;

        while(current != null){
            next_node = current.next;
            current.next = prev;
            prev = current;
            current = next_node;
        }

        return prev;
    }

    static void printList(ListNode head){
        System.out.println();
        while(head != null){
            System.out.print(head.value + "-->");
            head = head.next;
        }
        System.out.print("NULL\n");
    }

    public static void main(String[] args){
        ListNode head = makeList(Integer.parseInt(args[0]));
        printList(head);
        head = reverseList(head);
        printList(head);
    }
}