反转链表

题目：

输入一个链表，反转链表后，输出链表的所有元素。

struct ListNode
{
    int      value;
    ListNode *next;
};

void ReverseList( ListNode** pHead )
{
    if ( pHead == NULL || *pHead == NULL || (*pHead)->next == NULL )
        return ;
    ListNode* pPre = NULL;
    ListNode* pCur = *pHead;
    ListNode* pNext = (*pHead)->next;
    (*pHead)->next = NULL;

    while ( pNext != NULL )
    {
        pPre = pCur;
        pCur = pNext;
        pNext = pCur->next;

        pCur->next = pPre;
    }
    (*pHead) = pCur;
}