CJVUNGDATMOI (lqdoj) - SongLienThong

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

using pi32 = pair<int, int>;

const int N = 1e5 + 5;

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

int Num[N], Low[N], timer;
stack<pi32> st;
vector<int> best;

void Tajan(int u, int p) {
    Num[u] = Low[u] = ++timer;

    for (int v : graph[u]) {
        if (v == p) continue;

        if (Num[v]) {
            Low[u] = min(Low[u], Num[v]);
        }
        else {
            st.emplace(u, v);
            Tajan(v, u);
            Low[u] = min (Low[u], Low[v]);

            if (Low[v] >= Num[u]) {
                pi32 t;
                pi32 last = {u, v};
                vector<int> path;

                do {
                    t = st.top(); st.pop();
                    path.push_back(t.second);
                } while (t != last);
                path.push_back(u);

                if (path.size() > best.size())
                    swap(best, path);
            }
        }
    }
}

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

    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);
    }

    for (int i = 1; i <= n; ++i)
        if (!Num[i]) Tajan(i, i);

    cout << best.size() << '\n';
    reverse(best.begin(), best.end());
    for (int u : best)
        cout << u << ' ';

    return 0;
}