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OI-codes/AcWing/852/852.cpp

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#include <bits/stdc++.h>
using namespace std;
int n, m, u, v, w, dist[100005], cnt[100005];
vector<pair<int, int>> g[100005];
bool spfa() {
memset(dist, 0x3f, sizeof(dist));
queue<int> q;
for (int i = 1; i <= n; i++) {
q.push(i);
}
while (!q.empty()) {
int t = q.front();
q.pop();
for (auto i : g[t]) {
if (dist[i.first] > dist[t] + i.second) {
dist[i.first] = dist[t] + i.second;
cnt[i.first] = cnt[t] + 1;
if (cnt[i.first] >= n) return true;
q.push(i.first);
}
}
}
return false;
}
int main() {
cin >> n >> m;
for (int i = 0; i < m; i++) {
cin >> u >> v >> w;
g[u].push_back(make_pair(v, w));
}
cout << (spfa() ? "Yes" : "No") << endl;
return 0;
}