Road network

#include <iostream>
#include <vector>

using namespace std;

struct node {
	vector<int> out;
	vector<int> in;
};

void explore(int ni, node *nodes, bool *visited, bool reversed) {
	visited[ni] = true;
	int k = reversed ? nodes[ni].in.size() : nodes[ni].out.size();
	for (int i=0; i<k; ++i) {
		int nbr = reversed ? nodes[ni].in[i] : nodes[ni].out[i];
		if (!visited[nbr]) explore(nbr, nodes, visited, reversed);
	}
}

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);

	int n, m;
	cin >> n; cin >> m;

	node nodes[n];
	bool visited[n];
	for (int i=0; i<n; ++i) visited[i] = false;

	int a, b;
	for (int i=0; i<m; ++i) {
		cin >> a; cin >> b;
		nodes[a-1].out.push_back(b-1);
		nodes[b-1].in.push_back(a-1);
	}

	explore(0, nodes, visited, false);
	for (int i=0; i<n; ++i) {
		if (!visited[i]) {
			cout << "NO\n" << 1 << " " << (i+1) << "\n";
			return 0;
		}
	}

	for (int i=0; i<n; ++i) visited[i] = false;
	explore(0, nodes, visited, true);
	for (int i=0; i<n; ++i) {
		if (!visited[i]) {
			cout << "NO\n" << (i+1) << " " << "1\n";
			return 0;
		}
	}

	cout << "YES\n";

}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED