剑指offer—两个链表的第一个公共结点

/*
struct ListNode {
int val;
struct ListNode *next;
ListNode(int x) :
val(x), next(NULL) {
}
};*/
class Solution {
public:
ListNode* FindFirstCommonNode( ListNode *pHead1, ListNode *pHead2)
{
if(pHead1==NULL || pHead2==NULL)
return NULL;
ListNode* p1=pHead1;
while(p1!=NULL)
{
ListNode *p2=pHead2;
while(p2!=NULL)
{
if(p2==p1)
return p1;
p2=p2->next;
}
p1=p1->next;
}
return NULL;
}
};

classSolution {
public:
ListNode* FindFirstCommonNode( ListNode *pHead1, ListNode *pHead2) {
map<ListNode*, int> m;
ListNode *p = pHead1;
while(p != NULL) {
m[p] = 1;
p = p->next;
}
p = pHead2;
while(p != NULL) {
if(m[p]) {
return p;
}
p = p->next;
}
return NULL;
}
};