CJPHANCONG (lqdoj) - Khop

#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<int> graph[N];

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

void visit(int u, int p) {
    int NumChild = 0;
    Low[u] = Num[u] = ++Time;

    for (int v : graph[u])
        if (v != p) {
            if (Num[v] != 0)
                Low[u] = min(Low[u], Num[v]);
            else {
                visit(v, u);
                NumChild++;
                Low[u] = min(Low[u], Low[v]);

                if (u == p) {
                    if (NumChild >= 2)
                        CriticalNode[u] = true;
                } else {
                    if (Low[v] >= Num[u])
                        CriticalNode[u] = true;
                }
            }
        }
}

int main() {
#ifdef LOCAL
    freopen("in.txt", "r", stdin);
#else
    freopen("CJPHANCONG.inp", "r", stdin);
    freopen("CJPHANCONG.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);
    }

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

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

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

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