Finished c and d, e doesn't check for faulty arrangements

atcoder/beginner_contests/226/e.cpp

@@ -2,23 +2,53 @@
 
 using namespace std;
 
-void test_case(int tc){
+vector<bool> visitedNodes;
+vector<vector<int>> edgeList;
 
+void dfs(int start){
+    visitedNodes[start] = true;
+
+    for(int node : edgeList[start]){
+        if(!visitedNodes[node]){
+            dfs(node);
+        }
+    }
 }
 
-
-
 int main(){
     ios::sync_with_stdio(0);
     cin.tie(0);
 
-    int t;
-    cin >> t;
+    int n, m;
+    cin >> n >> m;
 
-    for(int tc = 1; tc <= t; ++tc){
-        test_case(tc);
+    if(n != m){
+        cout << 0 << endl;
+        return 0;
     }
 
+    visitedNodes.reserve(n+1);
+    edgeList.reserve(n+1);
+
+    for(int i = 1; i <= m; ++i){
+        int u, v;
+        cin >> u >> v;
+
+        edgeList[u].push_back(v);
+    }
+
+    long long result = 1;
+
+    for(int start = 1; start <= n; ++start){
+        if(!visitedNodes[start]){
+            result = (result * 2) % 998244353;
+
+            dfs(start);
+        }
+    }
+
+    cout << result;
+
     cout << flush;
 
     return 0;