flight routes check

CSES - CSES Problem Set/Graph_Algorithms/Flight_Routes_Check.cpp

@@ -0,0 +1,51 @@
+//  Flight Routes Check
+
+#include<bits/stdc++.h>
+
+using namespace std;
+
+void dfs(bitset<(int)1e5>& v, int s, vector<vector<int>> &g) {
+    v[s] = true;
+    for (auto &e: g[s]) {
+        if (!v[e]) {
+            dfs(v, e, g);
+        }
+    }
+}
+
+int main() {
+    int n, m; cin >> n >> m;
+    vector<vector<int>> g(n);
+    vector<vector<int>> r(n);
+    for (int i{}; i < m; i++) {
+        int a, b; cin >> a >> b; a--; b--;
+        g[a].push_back(b);
+        r[b].push_back(a);
+    }
+    bitset<(int)1e5> v = 0;
+    dfs(v, 0, g);
+    bitset<(int)1e5> v2 = 0;
+    if (v.count() != n) {
+        cout << "NO" << endl;
+        for (int i{}; i < n; i++) {
+            if (!v[i]) {
+                cout << 1 << " " << i + 1 << endl;
+                return 0;
+            }
+        }
+    } else {
+        dfs(v2, 0, r);
+        if (v2.count() != n) {
+            cout << "NO" << endl;
+            for (int i{}; i < n; i++) {
+                if (!v2[i]) {
+                    cout << i + 1 << " " << 1 << endl;
+                    return 0;
+                }
+            }
+        } else {
+            cout << "YES" << endl;
+        }
+    }
+    return 0;
+}