dsu_fast

struct DsuFast{
private:
    std::vector<int> w;
public:
    DsuFast(int n = 0) : w(n, -1) {}
    int leader(int u){
        if(w[u] < 0) return u;
        return w[u] = leader(w[u]);
    }
    int operator[](int u){ return leader(u); }
    int merge(int u, int v){
        u = leader(u);
        v = leader(v);
        if(u == v) return u;
        if(-w[u] < -w[v]) std::swap(u, v);
        w[u] += w[v];
        w[v] = u;
        return u;
    }
    int size(int u){ return -w[leader(u)]; }
    bool same(int u, int v){ return leader(u) == leader(v); }
    int addElem(){
        int res = int(w.size());
        w.push_back(-1);
        return res;
    }
};