206. Reverse Linked List

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode reverseList(ListNode head)
     {
        if(head == null)
        return null;

        ListNode prev = null;          
        ListNode curr = head;
        ListNode after = null;
        while(curr != null)
        {
          after = curr.next;
          curr.next = prev;
          prev = curr;
          curr = after;
        }
        return prev;


    }
}