CONNECT (lqdoj) - SoLienThong

#include <bits/stdc++.h>
using namespace std;

const int N = 1e5 + 5;

int n, nE;
vector<int> graph[N];

int visited[N];
vector<int> comp[N];

void DFS(int u, int id) {
    visited[u] = true;
    comp[id].push_back(u);

    for (int v: graph[u]) {
        if (!visited[v]) {
            DFS(v, id);
        }
    }
}

int main() {
#ifdef LOCAL
    freopen("in.txt", "r", stdin);
#else
    freopen("CONNECT.inp", "r", stdin);
    freopen("CONNECT.out", "w", stdout);
#endif // LOCAL
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    cin >> n >> nE;
    for (int i = 1; i <= nE; ++i) {
        int u, v; cin >> u >> v;
        graph[u].push_back(v);
        graph[v].push_back(u);
    }

    int id = 0;
    int ans = 0;
    for (int i = 1; i <= n; ++i) {
        if (!visited[i]) {
            DFS(i, ++id);
            ans++;
        }
    }

    cout << ans << '\n';
    for (int i = 1; i <= ans; ++i) {
        cout << comp[i].size() << ' ';
        for (int u: comp[i])
            cout << u << ' ';
        cout <<'\n';
    }

    return 0;
}
// https://lqdoj.edu.vn/problem/connect