The hints of the problem has given detailed information to implement the topological sorting algorithm. In fact, the toposort algorithm of the hint is the BFS version, which uses the indegrees of each node.

The code is as follows.

1 #include 
     
       2 #include 
      
        3 #include 
       
         4  5 using namespace std; 6  7 struct DirectedGraphNode { 8     int label; 9     vector
        
          neighbors;10     DirectedGraphNode(int i) : label(i) {}11 };12 13 vector
         
           init_graph(int nodes) {14     vector
          
            graph(nodes);15 for (int i = 0; i < nodes; i++)16 graph[i] = new DirectedGraphNode(i);17 return graph;18 }19 20 vector
           
             compute_indegree(vector
            
             & graph) {21 vector
             
               degrees(graph.size(), 0);22 for (int i = 0; i < (int)graph.size(); i++)23 for (int j = 0; j < (int)graph[i] -> neighbors.size(); j++)24 degrees[graph[i] -> neighbors[j]]++;25 return degrees;26 }27 28 bool noCycle(vector
              
               & graph) {29 vector
               
                 degrees = compute_indegree(graph);30 int nodes = graph.size();31 queue
                
                  zeros;32 for (int i = 0; i < (int)degrees.size(); i++)33 if (!degrees[i]) zeros.push(i);34 while (!zeros.empty()) {35 int zero = zeros.front();36 zeros.pop();37 for (int i = 0; i < (int)graph[zero] -> neighbors.size(); i++)38 if (--degrees[graph[zero] -> neighbors[i]] == 0)39 zeros.push(graph[zero] -> neighbors[i]);40 nodes--;41 }42 return nodes == 0;43 }44 45 int main(void) {46 int cases;47 scanf("%d", &cases);48 for (int i = 0; i < cases; i++) {49 int nodes, edges;50 scanf("%d %d", &nodes, &edges);51 vector
                 
                   graph = init_graph(nodes);52 int node, neigh;53 for (int j = 0; j < edges; j++) {54 scanf("%d %d", &node, &neigh);55 graph[node - 1] -> neighbors.push_back(neigh - 1);56 }57 if (noCycle(graph)) printf("Correct\n");58 else printf("Wrong\n");59 }60 return 0;61 }