Reverse a Singly LinkedList

 * Definition for singly-linked list.

 * public class ListNode {

 *     int val;

 *     ListNode next;

 *     ListNode(int x) {

 *         val = x;

 *         next = null;

 *     }

 * }

 */

public Class Solution{

    public static ListNode reverseList(ListNode head){

        if(head == null || head.next == null){

            return head;

        }

        ListNode next = head.next;

        head.next = null;

        while(next != null){

            ListNode temp = next.next;

            next.next = head;

            head = next;

            next = temp;

        }

        return head;

    }

}