在O（1）时间删除链表结点

//给定单向链表的头指针和一个结点指针，定义一个函数在O(1)时间删除该结点。
 1 struct ListNode  //结点结构
 {
   int m_nValue;
   ListNode* m_pNext;
 };

 void DeleteNode(ListNode** pListHead , ListNode* pToBeDeleted)
 {
   if (!pListHead || !pToBeDeleted)
   {
     return;
   }
   if (pToBeDeleted->m_pNext != NULL)
   {
     ListNode* pNext = pToBeDeleted->m_pNext ;
     pToBeDeleted->m_nValue = pNext->m_nValue;
     pToBeDeleted->m_pNext = pNext->m_pNext;
     delete pNext;
     pNext = NULL;
   }
   else if (*pListHead == pToBeDeleted)//只有一个结点
   {
23     delete pToBeDeleted;
     pToBeDeleted = NULL;
     *pListHead = NULL;
   }
   else //尾结点
   {
     ListNode* pNode = *pListHead ;
     while (pNode->m_pNext != pToBeDeleted)
     {
       pNode = pNode->m_pNext;
     }
     pNode->m_pNext = NULL ;
     delete pToBeDeleted;
     pToBeDeleted = NULL ;
   }
 }