两个链表的公共结点

1 struct ListNode 
2 {
3     int m_nValue;
4     ListNode* m_pNext;
5 }

 1 int GetListLength(ListNode* pHead)
 2 {
 3     int length = 0 ;
 4     while (pHead != NULL)
 5     {
 6         length++ ;
 7         pHead = pHead->m_pNext ;
 8     }
 9     return length ;
10 }
11 
12 ListNode* FindFirstCommonNode(ListNode* pHead1 , ListNode* pHead2)
13 {
14     int nLength1 = GetListLength(pHead1) ;
15     int nLength2 = GetListLength(pHead2) ;
16     int LengthDiff = nLength1 - nLength2 ;
17 
18     ListNode* pLongListHead = pHead1;
19     ListNode* pShortListHead = pHead2 ;
20     if (LengthDiff < 0)
21     {
22         LengthDiff = - LengthDiff ;
23         pLongListHead = pHead2;
24         pShortListHead = pHead1 ;    
25     }
26     for (int i = 0 ; i < LengthDiff ; i++)
27     {
28         pLongListHead = pLongListHead->m_pNext;
29     }
30     
31     while (pLongListHead != NULL && pShortListHead != NULL && pLongListHead != pShortListHead)
32     {
33         pLongListHead = pLongListHead->m_pNext;
34         pShortListHead = pShortListHead->m_pNext;
35     }
36 
37     ListNode* pFirstCommonNode = pLongListHead ;
38     return pFirstCommonNode;
39 }