/* -*- coding: utf-8 -*- * * 1023.cc: No.1023 Cyclic Tour - yukicoder */ #include<cstdio> #include<cstdlib> #include<cstring> #include<cmath> #include<iostream> #include<string> #include<vector> #include<map> #include<set> #include<stack> #include<list> #include<queue> #include<deque> #include<algorithm> #include<numeric> #include<utility> #include<complex> #include<functional> using namespace std; /* constant */ const int MAX_N = 100000; const int MAX_M = 200000; /* typedef */ typedef vector<int> vi; typedef queue<int> qi; typedef pair<int,int> pii; /* global variables */ vi nbrs[MAX_N]; int ps[MAX_N], cis[MAX_N], gids[MAX_N], pns[MAX_N]; pii es[MAX_M]; bool vstd[MAX_N]; /* subroutines */ /* main */ int main() { int n, m; scanf("%d%d", &n, &m); int en = 0; for (int i = 0; i < m; i++) { int a, b, c; scanf("%d%d%d", &a, &b, &c); a--, b--; if (c == 1) { nbrs[a].push_back(b); nbrs[b].push_back(a); } else es[en++] = pii(a, b); } memset(gids, -1, sizeof(gids)); int gn = 0; for (int st = 0; st < n; st++) if (gids[st] < 0) { ps[st] = -1; gids[st] = gn++; for (int u = st; u >= 0;) { if (cis[u] == 0) gids[u] = gids[st], vstd[u] = true; for (; cis[u] < nbrs[u].size(); cis[u]++) { int v = nbrs[u][cis[u]]; if (v != ps[u]) { if (gids[v] < 0) break; if (vstd[v]) { puts("Yes"); return 0; } } } if (cis[u] < nbrs[u].size()) { int v = nbrs[u][cis[u]++]; ps[v] = u, u = v; } else vstd[u] = false, u = ps[u]; } } //for (int u = 0; u < n; u++) printf(" %d", gids[u]); putchar('\n'); for (int u = 0; u < gn; u++) nbrs[u].clear(); for (int i = 0; i < en; i++) { int ga = gids[es[i].first], gb = gids[es[i].second]; if (ga != gb) { nbrs[ga].push_back(gb); pns[gb]++; } else { puts("Yes"); return 0; } } qi q; for (int u = 0; u < gn; u++) if (pns[u] == 0) q.push(u); int k = 0; while (! q.empty()) { int u = q.front(); q.pop(); k++; vi &nbru = nbrs[u]; for (vi::iterator vit = nbru.begin(); vit != nbru.end(); vit++) { int v = *vit; if (--pns[v] == 0) q.push(v); } } if (k != gn) puts("Yes"); else puts("No"); return 0; }