UnionFind.cpp

struct UnionFind {
        int n;
        vector<int> parent, rank, num;
        int find(int x) {
                if (parent[x] == x) return  x;
                return parent[x] = find(parent[x]);
        }
        UnionFind(int n_) {
                n = n_;
                parent.resize(n);
                for (int i = 0; i < n; i ++) parent[i] = i;
                rank.assign(n, 0);
                num.assign(n, 1);
        }
        void unite(int x, int y) {
                if ((x = find(x)) != (y = find(y))) {
                        if (rank[x] < rank[y]) {
                                parent[x] = y;
                                num[y] += num[x];
                        } else {
                                parent[y] = x;
                                if (rank[x] == rank[y]) rank[x] ++;
                                num[x] += num[y];
                        }
                        n --;
                }
        }
        bool same(int x, int y) { return find(x) == find(y); }
        int get() { return n; }
        int get(int x) { return num[find(x)]; }
};