面试题13：在O(1)时间删除链表节点

注意分情况讨论：

1. 要删除的不是尾节点

2. 链表只有一个节点

3. 链表中有多个节点，删除尾节点

 1 void DeleteNode(ListNode** pListHead, ListNode* pToBeDeleted)
 2 {
 3     if(!pListHead || !pToBeDeleted)
 4         return;
 5 
 6     // 要删除的结点不是尾结点
 7     if(pToBeDeleted->m_pNext != NULL)
 8     {
 9         ListNode* pNext = pToBeDeleted->m_pNext;
10         pToBeDeleted->m_nValue = pNext->m_nValue;
11         pToBeDeleted->m_pNext = pNext->m_pNext;
12  
13         delete pNext;
14         pNext = NULL;
15     }
16     // 链表只有一个结点，删除头结点（也是尾结点）
17     else if(*pListHead == pToBeDeleted)
18     {
19         delete pToBeDeleted;
20         pToBeDeleted = NULL;
21         *pListHead = NULL;
22     }
23     // 链表中有多个结点，删除尾结点
24     else
25     {
26         ListNode* pNode = *pListHead;
27         while(pNode->m_pNext != pToBeDeleted)
28         {
29             pNode = pNode->m_pNext;            
30         }
31  
32         pNode->m_pNext = NULL;
33         delete pToBeDeleted;
34         pToBeDeleted = NULL;
35     }
36 }