反转链表

输入一个链表，反转链表后，输出链表的所有元素。

/*struct ListNode {    int val;    struct ListNode *next;    ListNode(int x) :            val(x), next(NULL) {    }};*/class Solution {public:    ListNode* ReverseList(ListNode* pHead) {        ListNode* pre = NULL;        ListNode* next = NULL;        while(pHead)        {            next = pHead->next;            pHead->next = pre;            pre = pHead;            pHead = next;           }        return pre;    }};