947

class Solution {
int components=0;
unordered_map<int, int> parent, rank;
public:
    int findParent(int x){
        if(!parent.count(x)){
            parent[x] = x;
            rank[x] = 0;
            components++;
        }
        return (parent[x] == x) ? x : (parent[x] = findParent(parent[x]));
    }

    void unionSet(int x, int y){
        int px = findParent(x);
        int py = findParent(y);
        if(px != py){
            components--;
            if(rank[x] > rank[y]){
                parent[py] = px;
            }
            else{
                parent[px] = py;
                rank[y]++;
            }
        }
    }

    int removeStones(vector<vector<int>>& stones) {
        for(vector<int> stone: stones)
            unionSet(stone[0], ~stone[1]);
        return stones.size()-components;
    }
};