#include <cstdio> #include <vector> using namespace std; const int maxN = 500000; int state[maxN + 1], banned_vertex; bool found_cycle, res[maxN + 1]; vector <int> G[maxN + 1]; void dfs(int v) { if (found_cycle) return; state[v] = 1; for (int i=0; i<G[v].size(); i++) { int u = G[v][i]; if ((u == banned_vertex) or (state[u] == 2)) continue; if (state[u] == 1) found_cycle = 1; else dfs(u); } state[v] = 2; } int main() { int n, m; scanf ("%d%d", &n, &m); while (m--) { int a, b; scanf ("%d%d", &a, &b); G[a].push_back(b); } for (banned_vertex = 0; banned_vertex <= n; banned_vertex++) { for (int i=1; i<=n; i++) { if ((i == banned_vertex) or (state[i] == 2)) continue; dfs(i); if (found_cycle) break; } res[banned_vertex] = !found_cycle; found_cycle = 0; fill(state, state + n + 1, 0); } if (res[0]) { printf("NIE\n"); return 0; } int res_amount = 0; for (int i=1; i<=n; i++) res_amount += res[i]; printf("%d\n", res_amount); for (int i=1; i<=n; i++) { if (res[i]) printf("%d ", i); } 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 | #include <cstdio> #include <vector> using namespace std; const int maxN = 500000; int state[maxN + 1], banned_vertex; bool found_cycle, res[maxN + 1]; vector <int> G[maxN + 1]; void dfs(int v) { if (found_cycle) return; state[v] = 1; for (int i=0; i<G[v].size(); i++) { int u = G[v][i]; if ((u == banned_vertex) or (state[u] == 2)) continue; if (state[u] == 1) found_cycle = 1; else dfs(u); } state[v] = 2; } int main() { int n, m; scanf ("%d%d", &n, &m); while (m--) { int a, b; scanf ("%d%d", &a, &b); G[a].push_back(b); } for (banned_vertex = 0; banned_vertex <= n; banned_vertex++) { for (int i=1; i<=n; i++) { if ((i == banned_vertex) or (state[i] == 2)) continue; dfs(i); if (found_cycle) break; } res[banned_vertex] = !found_cycle; found_cycle = 0; fill(state, state + n + 1, 0); } if (res[0]) { printf("NIE\n"); return 0; } int res_amount = 0; for (int i=1; i<=n; i++) res_amount += res[i]; printf("%d\n", res_amount); for (int i=1; i<=n; i++) { if (res[i]) printf("%d ", i); } return 0; } |