Road network

#include <iostream>
#include <vector>
using namespace std;

void dfs(vector<vector<int>> &G, vector<bool> &v, int node) {
    v[node] = true;
    for (int &nxt : G[node])
        if (!v[nxt]) dfs(G, v, nxt);
}

int main () {
    int n, m;
    cin >> n >> m;

    vector<vector<int>> G(n+1), R(n+1);

    for (int i = 0; i < m; ++i) {
        int a, b;
        cin >> a >> b;

        G[a].push_back(b);
        R[b].push_back(a);
    }

   vector<bool> visited(n+1, false);
   vector<bool> visitedR(n+1, false);

    dfs(G, visited, 1);
    for (int i=1; i <= n; ++i)
        if (!visited[i]) {
            cout << "NO" << endl << 1 << ' ' << i << endl;
            return 0;
        }
    dfs(R, visitedR, 1);
    for (int i=1; i <= n; ++i)
        if (!visitedR[i]) {
            cout << "NO" << endl << i << ' ' << 1 << endl;
            return 0;
        }

    cout << "YES" << endl;

}

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