CJXAYDUNG (lqdoj) - Cau

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

using i64 = long long;
using pi32 = pair<int, int>;
using pi64 = pair<i64, i64>;

const int N = 1e5 + 5;

int n, nE;
vector<pi32> graph[N];

int CriticalEdge = 0;
bool isCutEdge[N];
int Num[N], Low[N], Time = 0;

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

    for (int i = 0; i < graph[u].size(); ++i) {
        int v = graph[u][i].first;
        int id = graph[u][i].second;

        if (v == p) continue;

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

            isCutEdge[id] |= Low[v] > Num[u];
        }
    }
}

int main() {
#ifdef LOCAL
    freopen("in.txt", "r", stdin);
#else
    freopen("CJXAYDUNG.inp", "r", stdin);
    freopen("CJXAYDUNG.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, i});
        graph[v].push_back({u, i});
    }

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

    int Count = 0;
    for (int i = 1; i <= n; i++)
        if (isCutEdge[i]) Count++;

    cout << Count << '\n';
    for (int i = 1; i <= n; i++)
        if (isCutEdge[i])
            cout << i << ' ';

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