#include #include #include #include #include #include #include using namespace std; typedef long long ll; const int N_MAX = 200000; int N; bool used[N_MAX]; int idx[N_MAX]; vector vs; vector buf; vector G[N_MAX]; vector G_inv[N_MAX]; vector> ans; void clear(){ for(int i = 0; i < N; i++) used[i] = false; } void dfs1(int v){ used[v] = true; for(int i = 0; i < G[v].size(); i++){ if(!used[G[v][i]]) dfs1(G[v][i]); } vs.push_back(v); } void dfs2(int v, int k){ used[v] = true; idx[v] = k; for(int i = 0; i < G_inv[v].size(); i++){ if(!used[G_inv[v][i]]) dfs2(G_inv[v][i], k); } buf.push_back(v); } // Nを初期化してからつかうこと。G_invも作成されていること。 void scc(){ for(int i = 0; i < N; i++){ if(!used[i]) dfs1(i); } clear(); int cur = 0; for(int i = vs.size()-1; i >= 0; i--){ if(!used[vs[i]]) { dfs2(vs[i], cur); cur++; ans.push_back(buf); buf.clear(); } } } struct UnionFind { vector data; UnionFind(int size) : data(size, -1) { } bool unionSet(int x, int y) { x = root(x); y = root(y); if (x != y) { if (data[y] < data[x]) swap(x, y); data[x] += data[y]; data[y] = x; } return x != y; } bool findSet(int x, int y) { return root(x) == root(y); } int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); } int size(int x) { return -data[root(x)]; } }; int M; int a[200000], b[200000], c[200000]; int main(){ ios::sync_with_stdio(false); cin.tie(0); cout << setprecision(10) << fixed; cin >> N >> M; UnionFind uf(N); bool ok = false; for(int i = 0; i < M; i++){ cin >> a[i] >> b[i] >> c[i]; a[i]--; b[i]--; if(c[i] == 1){ if(uf.findSet(a[i], b[i])) ok = true; uf.unionSet(a[i], b[i]); } } if(ok) { cout << "Yes" << endl; return 0; } for(int i = 0; i < M; i++){ int ar = uf.root(a[i]); int br = uf.root(b[i]); if(c[i] == 2){ if(ar == br) ok = true; G[ar].push_back(br); G_inv[br].push_back(ar); } } if(ok) { cout << "Yes" << endl; return 0; } scc(); for(auto v : ans){ if(v.size() > 1) ok = true; } cout << (ok ? "Yes" : "No") << endl; }