From 55a83b71b51445f29cb07581f545f96d048a998d Mon Sep 17 00:00:00 2001
From: Ren Baoshuo <i@baoshuo.ren>
Date: Wed, 11 Aug 2021 21:20:06 +0800
Subject: [PATCH] =?UTF-8?q?852.=20spfa=E5=88=A4=E6=96=AD=E8=B4=9F=E7=8E=AF?=
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https://www.acwing.com/problem/content/submission/code_detail/7062672/
---
 AcWing/852/852.cpp | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 AcWing/852/852.cpp

diff --git a/AcWing/852/852.cpp b/AcWing/852/852.cpp
new file mode 100644
index 00000000..03f2120c
--- /dev/null
+++ b/AcWing/852/852.cpp
@@ -0,0 +1,37 @@
+#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;
+}