Erősen összefüggővé alakítás - AK423Q

#include <iostream>
#include <vector>
#include <set>

using namespace std;

int L[10000];
int P[10000];
int index;
bool visited[10000];
vector<int> graph[10000];
vector<int> graphT[10000];

void dfs(int node) {
	for (int n : graph[node]) {
		if (!visited[n]) {
			visited[n] = true;
			dfs(n);
		}
	}
	L[index--] = node;
}

void dfs2(int node) {
	for (int n : graphT[node]) {
		if (P[n] == -1) {
			P[n] = P[node];
			dfs2(n);
		}
	}
}

int main() {
	int N, M;
	cin >> N >> M;
	int p, q;
	for (int i = 0; i < M; i++) {
		cin >> p >> q;
		p--;
		q--;
		graph[p].push_back(q);
		graphT[q].push_back(p);
	}

	for (int i = 0; i < N; i++) {
		visited[i] = false;
	}
	index = N - 1;
	for (int i = 0; i < N; i++) {
		if (!visited[i]) {
			visited[i] = true;
			dfs(i);
		}
	}

	for (int i = 0; i < N; i++) {
		P[i] = -1;
	}
	int ind = 0;
	for (int i = 0; i < N; i++) {
		if (P[L[i]] == -1) {
			P[L[i]] = ind++;
			dfs2(L[i]);
		}
	}

	if (ind == 1) {
		cout << "0 0" << endl;
		return 0;
	}

	set<int> in[ind], out[ind];
	for (int i = 0; i < N; i++) {
		for (int j : graph[i]) {
			if (P[i] != P[j]) {
				out[P[i]].insert(P[j]);
				in[P[j]].insert(P[i]);
			}
		}
	}
	int good_in, good_out;
	for (int i = 0; i < ind; i++) {
		if (in[i].size() == 0) {
			good_in = i;
		}
		if (out[i].size() == 0) {
			good_out = i;
		}
	}
	int node_in, node_out;
	for (int i = 0; i < N; i++) {
		if (P[i] == good_in) {
			node_in = i;
		}
		if (P[i] == good_out) {
			node_out = i;
		}
	}
	cout << node_out + 1 << " " << node_in + 1 << endl;

	return 0;
}