CJSCONNECT (lqdoj) - LienThongManh

#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;
const int oo = 0x3c3c3c3c;

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

int Num[N], Low[N];
stack<int> st;

int Count = 0;
vector<int> ans[N];

void visit(int u) {
    static int time = 0;
    Low[u] = Num[u] = ++time;
    st.push(u);

    for (int v : graph[u])
        if (Num[v])
            Low[u] = min(Low[u], Num[v]);
        else {
            visit(v);
            Low[u] = min(Low[u], Low[v]);
        }

    if (Num[u] == Low[u]) {
        ++Count;
        int v;
        do {
            v = st.top(); st.pop();

            ans[Count].push_back(v);
            Num[v] = Low[v] = oo;
        } while (v != u);
    }
}

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

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

    int id = 0, maxLen = 0;
    for(int i = 1; i <= Count; ++i) {
        if (maxLen < (int)ans[i].size()) {
            maxLen = ans[i].size();
            id = i;
        }
    }

    sort(ans[id].begin(), ans[id].end());
    cout << maxLen << '\n';
    for (int u : ans[id])
        cout << u << ' ';

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

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

const int N = 1e5 + 5;

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

int Num[N], Low[N];
bool visited[N];
stack<int> st;

int Count = 0;
vector<int> ans[N];

void Tajan(int u) {
    static int time = 0;
    Num[u] = Low[u] = ++time;
    st.push(u);
    visited[u] = true;

    for (int v : graph[u]) {
        if (Num[v] == -1) {
            Tajan(v);
            Low[u] = min(Low[u], Low[v]);
        }
        else if(visited[v])
            Low[u] = min(Low[u], Num[v]);
    }

    if (Num[u] == Low[u]) {
        ++Count;
        int v;
        do {
            v = st.top(); st.pop();

            ans[Count].push_back(v);
            visited[v] = false;
        } while (v != u);
    }
}

void solve() {
    for (int i = 1; i <= n; i++) {
        Num[i] = Low[i] = -1;
        visited[i] = false;
    }

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

    int id = 0, maxLen = 0;
    for(int i = 1; i <= Count; ++i) {
        if (maxLen < (int)ans[i].size()) {
            maxLen = ans[i].size();
            id = i;
        }
    }

    sort(ans[id].begin(), ans[id].end());
    cout << maxLen << '\n';
    for (int u : ans[id])
        cout << u << ' ';
}

int main() {
#ifdef LOCAL
   freopen("in.txt", "r", stdin);
#else
    freopen("CJSCONNECT.inp", "r", stdin);
    freopen("CJSCONNECT.out", "w", stdout);
#endif
    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);
    }

    solve();

    return 0;
}
*/