#include using namespace std; using i64 = long long; #define rep(i,s,e) for(i64 (i) = (s);(i) < (e);(i)++) #define all(x) x.begin(),x.end() template static inline std::vector ndvec(size_t&& n, T val) noexcept { return std::vector(n, std::forward(val)); } template static inline auto ndvec(size_t&& n, Tail&&... tail) noexcept { return std::vector(tail)...))>(n, ndvec(std::forward(tail)...)); } template struct chain { Cond cond; chain(Cond cond) : cond(cond) {} bool operator()(T& a, const T& b) const { if(cond(a, b)) { a = b; return true; } return false; } }; template chain make_chain(Cond cond) { return chain(cond); } #include using namespace std; using i64 = long long; vector strongly_connected_components(const vector>& g) { i64 n = g.size(); vector> rg(n); for(int i = 0;i < n;i++) { for(auto j: g[i]) { rg[j].push_back(i); } } vector vis(n,false); vector vs; vector res(n,-1); function dfs = [&](int v) { vis[v] = true; for(auto& t : g[v]) { if(!vis[t]) dfs(t); } vs.push_back(v); }; function rdfs = [&](int v,int k) { vis[v] = true; res[v] = k; for(auto to : rg[v]) { if(!vis[to]) rdfs(to,k); } }; for(int i = 0;i < n;i++) { if(!vis[i]) dfs(i); } vis.assign(n,false); int k = 0; for(int i = n - 1;i >= 0;i--) { if(!vis[vs[i]]) rdfs(vs[i] , k++); } return res; } #include #include using namespace std; struct union_find { vector par; vector rank; union_find(int n) : par(n) , rank(n) { for(int i = 0;i < n;i++) par[i] = i; } int root(int i) { return par[i] == i ? i : par[i] = root(par[i]); } /* unite x, y return parent */ int unite(int x,int y) { x = root(x); y = root(y); if(x == y) return -1; if(rank[x] < rank[y]) { par[x] = y; return y; } else { par[y] = x; if(rank[x] == rank[y]) rank[x]++; return x; } } }; vector> G; int main() { i64 N, M; cin >> N >> M; std::vector> vec; union_find uf(N); rep(i,0,M) { i64 a, b, c; cin >> a >> b >> c; a--; b--; if(c == 1) { if(uf.root(a) == uf.root(b)) { cout << "Yes" << endl; return 0; } uf.unite(a, b); } else { vec.push_back({ a, b }); } } G.resize(N); for(auto e: vec) { i64 a = uf.root(e.first); i64 b = uf.root(e.second); if(a == b) { cout << "Yes" << endl; return 0; } G[a].push_back(b); } auto res = strongly_connected_components(G); auto ans = *std::max_element(all(res)); if(ans + 1 == N) { cout << "No" << endl; } else { cout << "Yes" << endl; } }