func_code_string: #include <bits/stdc++.h>   using namespace std;   template <typename T>   void read(T &x) {     x = 0;     int fl = 1;     char ch = getchar();     while (ch <  0  || ch >  9 ) {       if (ch ==  - ) fl = -1;       ch = getchar();     }     while (ch >=  0  && ch <=  9 ) {       x = (x << 1) + (x << 3) + ch -  0 ;       ch = getchar();     }     x *= fl;   }   template <typename T, typename... Args>   inline void read(T &t, Args &...args) {     read(t);     read(args...);   }   const int N = 200005;   int T, n, m;   vector<int> edge[N];   int main() {     for (read(T); T; T--) {       read(n, m);       for (int i = 1; i <= n; i++) edge[i].clear();       vector<int> deg(n + 1), level(n + 1, 1);       for (int i = 1; i <= m; i++) {         int u, v;         read(u, v);         edge[u].emplace_back(v);         deg[v]++;       }       vector<int> ans;       for (int i = 1; i <= n; i++) {         if (level[i] == 3) {           ans.emplace_back(i);           continue;         }         for (auto &to : edge[i]) level[to] = max(level[to], level[i] + 1);       }       printf( %d n , (int)ans.size());       for (auto &k : ans) printf( %d  , k);       puts(  );     }     return 0;   }   