剑指offer——两个链表的第一个公共结点

#include <iostream>
using namespace std;

ListNode
{
int m_data;
ListNode *m_next;
};

unsigned int GetListLength(ListNode* pHead)
{
unsigned int nLength=0;
ListNode* pNode=pHead;
while(pNode!=NULL)
{
++nLength;
pNode=pNode->m_next;
}
}

ListNode* FindFirstCommonNode(ListNode* pHead1,ListNode* pHead2)
{
unsigned int nLength1=GetListLength(pHead1);
unsigned int nLength2=GetListLength(pHead2);
int nLengthDif=nLength1-nLength2;
ListNode* pListLong=pHead1;
ListNode* pListShort=pHead2;
if (nLength2>nLength1)
{
pListLong=pHead2;
pListShort=pHead1;
nLengthDif=-nLengthDif;
}
for (int i=0;i<nLengthDif;i++)
{
pListLong=pListLong->m_next;
}
while((pListLong!=NULL)&&(pListShort!=NULL)&&(pListLong!=pListShort))
{
pListLong=pListLong->m_next;
pListShort=pListShort->m_next;
}
ListNode* pFirstCommonNode=pListLong;
return pFirstCommonNode;
}