struct ListNode {
	int val;
	struct ListNode *next;
	ListNode(int x) :
			val(x), next(NULL) {
	}
};*/
class Solution {
public:
    ListNode* FindFirstCommonNode( ListNode* pHead1, ListNode* pHead2) {
        map<ListNode *,int>a;
        while(pHead1){
            a[pHead1]=1;
            pHead1=pHead1->next;
        }
        while(pHead2){
            if(a[pHead2])
                return pHead2;
            pHead2=pHead2->next;
        }
        return NULL;
    }
};