/**
 knakul853
 **/
class Solution {
public:
    ListNode* reverseList(ListNode* head) {

        ListNode* pre = NULL;

        while( head )
        {
            ListNode* save_next = head->next;
            head->next = pre;
            pre = head;
            head  = save_next;
        }

        return pre;
    }
};