/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    int numComponents(ListNode* head, vector<int>& G) {
        // save g in set
        unordered_set<int> s(G.begin(), G.end());
        int result = 0;

        if(!head)
            return result;

        auto p = head;
        auto q = head->next;

        while(q){
            if(s.find(q->val) != s.end() && s.find(p->val) != s.end()){
                result += 1;
                cout<<q->val<<" "<<p->val<<endl;
            }
            p = q;
            q = q->next;
        }

        return G.size() - result;
    }
};