找出链表的第一个公共结点 【微软面试100题 第六十二题】

　　

#include <iostream>

using namespace std;

typedef struct ListNode
{
struct ListNode *next;
int data;
}ListNode;

void InitList(ListNode **head1,ListNode **head2);
ListNode *FindFirstCommonNode(ListNode *pHead1,ListNode *pHead2);
void PrintList(ListNode *h);

int main(void)
{
ListNode *h1 = NULL,*h2 = NULL;

InitList(&h1,&h2);
cout << "h1为：";
PrintList(h1);
cout << "h2为：";
PrintList(h2);
ListNode *pFirstCommonNode = FindFirstCommonNode(h1,h2);
if(pFirstCommonNode)
cout << "第一个公共结点的值为：" << pFirstCommonNode->data << endl;
else
cout <<"没有公共结点" << endl;
return 0;
}
void PrintList(ListNode *h)
{
while(h!=NULL)
{
cout << h->data << " ";
h = h->next;
}
cout << endl;
}
unsigned int GetListLength(ListNode *pHead)
{
unsigned int nLen = 0;
ListNode *pNode = pHead;
while(pNode != NULL)
{
++nLen;
pNode = pNode->next;
}
return nLen;
}
ListNode *FindFirstCommonNode(ListNode *pHead1,ListNode *pHead2)
{
if(pHead1==NULL || pHead2==NULL)
return NULL;
unsigned int len1 = GetListLength(pHead1);
unsigned int len2 = GetListLength(pHead2);
int lenDif = len1-len2;
ListNode *pListHeadLong = pHead1;
ListNode *pListHeadShort = pHead2;
if(len1<len2)
{
pListHeadLong = pHead2;
pListHeadShort = pHead1;
lenDif = len2-len1;
}
for(int i = 0;i<lenDif;i++)
pListHeadLong = pListHeadLong->next;
while((pListHeadLong!=NULL) && (pListHeadShort!=NULL) && (pListHeadLong!=pListHeadShort))
{
pListHeadLong = pListHeadLong->next;
pListHeadShort = pListHeadShort->next;
}
return pListHeadLong;
}
//head1:1-->5-->9-->NULL
//head2:2-->4-->10-->5-->9-->NULL
void InitList(ListNode **head1,ListNode **head2)
{
ListNode *tmp = new ListNode,*store;
tmp->data = 1;
*head1 = tmp;

tmp = new ListNode;
tmp->data = 5;
store = tmp;
(*head1)->next = tmp;

ListNode *tmp1 = new ListNode;
tmp1->data = 9;
tmp1->next = NULL;
tmp->next = tmp1;

tmp = new ListNode;
tmp->data = 2;
*head2 = tmp;

tmp = new ListNode;
tmp->data = 4;
(*head2)->next = tmp;

tmp1 = new ListNode;
tmp1->data = 10;
tmp1->next = store;
tmp->next = tmp1;
}