面试题04：找出两个单向链表的第一个公共节点

struct ListNode
{
int       Key;
ListNode*   pNext;
};

ListNode* FindFirstCommonNode(ListNode* list1,ListNode* list2){
ListNode* pCommon=NULL;
if(list1==NULL || list2==NULL){
return pCommon;
}
int len1=0;
int len2=0;
ListNode* pNode1=list1;
ListNode* pNode2=list2;
while(pNode1!=NULL){
len1++;
pNode1=pNode1->pNext;
}
while(pNode2!=NULL){
len2++;
pNode2=pNode2->pNext;
}

pNode1=list1;
pNode2=list2;
if(len1<len2){
//Swap(pNode1,pNode2);
ListNode* temp=pNode1;
pNode1=pNode2;
pNode2=temp;
}
int m=len1>len2?len1:len2;
int n=len1>len2?len2:len1;
for(int i=0;i<m-n;i++){
pNode1=pNode1->pNext;
}

while(pNode1!=NULL && pNode1->Key!=pNode2->Kye){
pNode1=pNode2->pNext;
pNode2=pNode2->pNext;
}
pCommon=pNode1;
return pCommon;
}

#include <iostream>
using namespace std;

#define NULL 0

struct ListNode
{
int       Key;
ListNode*   pNext;
};

ListNode* FindFirstCommonNode(ListNode* list1,ListNode* list2){
ListNode* pCommon=NULL;
if(list1==NULL || list2==NULL){
return pCommon;
}
int len1=0;
int len2=0;
ListNode* pNode1=list1;
ListNode* pNode2=list2;
while(pNode1!=NULL){
len1++;
pNode1=pNode1->pNext;
}
while(pNode2!=NULL){
len2++;
pNode2=pNode2->pNext;
}

pNode1=list1;
pNode2=list2;
if(len1<len2){
//Swap(pNode1,pNode2);
ListNode* temp=pNode1;
pNode1=pNode2;
pNode2=temp;
}
int m=len1>len2?len1:len2;
int n=len1>len2?len2:len1;
for(int i=0;i<m-n;i++){
pNode1=pNode1->pNext;
}

while(pNode1!=NULL && pNode1->Key!=pNode2->Key){
pNode1=pNode2->pNext;
pNode2=pNode2->pNext;
}
pCommon=pNode1;
return pCommon;
}

ListNode* CreateNode(int key,ListNode* next=NULL){
ListNode* node=new ListNode;
node->Key=key;
node->pNext=next;
return node;
}

void PrintList(ListNode* head){
ListNode* p=head;
while(p!=NULL){
cout<<p->Key<<ends;
p=p->pNext;
}
}

main(){

ListNode* e=CreateNode(5);
ListNode* d=CreateNode(4,d);

ListNode* c1=CreateNode(3,d);
ListNode* b1=CreateNode(2,c1);
ListNode* a1=CreateNode(1,b1);

ListNode* c2=CreateNode(31,d);
ListNode* b2=CreateNode(21,c2);
ListNode* a2=CreateNode(11,b2);

//  PrintList(a1);
cout<<endl;
PrintList(a2);
cout<<endl;

//  ListNode* pcommon=FindFirstCommonNode(a1,a2);
//  cout<<pcommon->Key<<endl;

return 0;
}