`
class Solution {
public:
ListNode findFirstCommonNode(ListNode headA, ListNode *headB) {
map[HTML_REMOVED] phash;

    int n =0;
    for(auto p = headA; p ; p = p->next)
    {
        phash[p] = n;
        n++;
    }

    for(auto p = headB; p ; p = p->next)
    {
        if(phash.find(p) != phash.end())
            return p;
    }
    return nullptr;

}

};`

第一次遍历，建立hash,
第二次遍历，查找表