#include <iostream> #include <list> using namespace std; // Graph class represents a directed graph using adjacency list representation class Graph { list<int> *adj; // Pointer to an array containing adjacency lists void DFSUtil(int v, bool visited[]); // A function used by DFS public: int V; // No. of vertices Graph(int V); // Constructor void addEdge(int v, int w); // function to add an edge to graph void DFS(int v); // DFS traversal of the vertices reachable from v }; Graph::Graph(int V) { this->V = V; adj = new list<int>[V]; } void Graph::addEdge(int v, int w) { adj[v].push_back(w); // Add w to v’s list. } int ile = 0; bool *required; bool *DFSed; void Graph::DFSUtil(int v, bool visited[]) { visited[v] = true; //cout<<"DFS("<<v<<")"<<endl; DFSed[v]=1; // Mark the current node as visited and print it // Recur for all the vertices adjacent to this vertex list<int>::iterator i; for(i = adj[v].begin(); i != adj[v].end(); ++i){ if(visited[*i]){ // mamy cykl for (int j = 0; j < V; ++j) { required[j]=required[j]&visited[j]; //if(visited[j])cout<<j<<" "; } //cout<<endl; ile++; } else{ DFSUtil(*i, visited); } } visited[v]=false; } // DFS traversal of the vertices reachable from v. It uses recursive DFSUtil() void Graph::DFS(int v) { // Mark all the vertices as not visited bool *visited = new bool[V]; for(int i = 0; i < V; i++) visited[i] = false; // Call the recursive helper function to print DFS traversal DFSUtil(v, visited); } int n,m, v1, v2; int main() { ios_base::sync_with_stdio(0); cin>>n>>m; // Create a graph given in the above diagram Graph g(n); for (int i = 0; i < m; ++i) { cin>>v1>>v2; v1--; v2--; g.addEdge(v1, v2); } required = new bool[g.V]; DFSed = new bool[g.V]; for(int i = 0; i < g.V; i++){ required[i] = 1; DFSed[i]=0; } for (int i = 0; i < n; ++i) { //if(!DFSed[i]){ g.DFS(i); // cout<<"DFS("<<i<<endl; //} } int ilef=0; for (int i = 0; i < g.V; ++i) { if (required[i]) { ilef++; } } if(ile>0){ cout<<ilef<<endl; for(int i = 0; i < g.V; i++) if(required[i]) cout<<i+1<<" "; } else cout<<"NIE"<<endl; return 0; }
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 | #include <iostream> #include <list> using namespace std; // Graph class represents a directed graph using adjacency list representation class Graph { list<int> *adj; // Pointer to an array containing adjacency lists void DFSUtil(int v, bool visited[]); // A function used by DFS public: int V; // No. of vertices Graph(int V); // Constructor void addEdge(int v, int w); // function to add an edge to graph void DFS(int v); // DFS traversal of the vertices reachable from v }; Graph::Graph(int V) { this->V = V; adj = new list<int>[V]; } void Graph::addEdge(int v, int w) { adj[v].push_back(w); // Add w to v’s list. } int ile = 0; bool *required; bool *DFSed; void Graph::DFSUtil(int v, bool visited[]) { visited[v] = true; //cout<<"DFS("<<v<<")"<<endl; DFSed[v]=1; // Mark the current node as visited and print it // Recur for all the vertices adjacent to this vertex list<int>::iterator i; for(i = adj[v].begin(); i != adj[v].end(); ++i){ if(visited[*i]){ // mamy cykl for (int j = 0; j < V; ++j) { required[j]=required[j]&visited[j]; //if(visited[j])cout<<j<<" "; } //cout<<endl; ile++; } else{ DFSUtil(*i, visited); } } visited[v]=false; } // DFS traversal of the vertices reachable from v. It uses recursive DFSUtil() void Graph::DFS(int v) { // Mark all the vertices as not visited bool *visited = new bool[V]; for(int i = 0; i < V; i++) visited[i] = false; // Call the recursive helper function to print DFS traversal DFSUtil(v, visited); } int n,m, v1, v2; int main() { ios_base::sync_with_stdio(0); cin>>n>>m; // Create a graph given in the above diagram Graph g(n); for (int i = 0; i < m; ++i) { cin>>v1>>v2; v1--; v2--; g.addEdge(v1, v2); } required = new bool[g.V]; DFSed = new bool[g.V]; for(int i = 0; i < g.V; i++){ required[i] = 1; DFSed[i]=0; } for (int i = 0; i < n; ++i) { //if(!DFSed[i]){ g.DFS(i); // cout<<"DFS("<<i<<endl; //} } int ilef=0; for (int i = 0; i < g.V; ++i) { if (required[i]) { ilef++; } } if(ile>0){ cout<<ilef<<endl; for(int i = 0; i < g.V; i++) if(required[i]) cout<<i+1<<" "; } else cout<<"NIE"<<endl; return 0; } |