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
 2 {
 3   int m_nValue;
 4   ListNode* m_pNext;
 5 };
 6 
 7 void DeleteNode(ListNode** pListHead , ListNode* pToBeDeleted)
 8 {
 9   if (!pListHead || !pToBeDeleted)
10   {
11     return;
12   }
13   if (pToBeDeleted->m_pNext != NULL)
14   {
15     ListNode* pNext = pToBeDeleted->m_pNext ;
16     pToBeDeleted->m_nValue = pNext->m_nValue;
17     pToBeDeleted->m_pNext = pNext->m_pNext;
18     delete pNext;
19     pNext = NULL;
20   }
21   else if (*pListHead == pToBeDeleted)//只有一个结点
22   {
23     delete pToBeDeleted;
24     pToBeDeleted = NULL;
25     *pListHead = NULL;
26   }
27   else //尾结点
28   {
29     ListNode* pNode = *pListHead ;
30     while (pNode->m_pNext != pToBeDeleted)
31     {
32       pNode = pNode->m_pNext;
33     }
34     pNode->m_pNext = NULL ;
35     delete pToBeDeleted;
36     pToBeDeleted = NULL ;
37   }
38 }
39 
40