New: total 2 codes

FZOI/【模板】负环.cpp

@@ -0,0 +1,63 @@
+#include <bits/stdc++.h>
+#define lo long long
+#define INF 0x3f3f3f3f3f3f3f3fl
+#define LLM LONG_LONG_MAX
+
+using namespace std;
+const lo N = 1e5 + 10;
+/*
+    toothless. #17
+    @fredcss_dev
+*/
+
+struct Edge {
+	lo u, v, w;
+};
+
+lo t, n, m;
+lo c, p, W;
+	
+vector<Edge> edge;
+
+lo dis[N], u, v, w;
+
+bool bellmanford(lo n, lo s)
+{
+	memset(dis, 0x3f, (n + 1) * sizeof(lo));
+	dis[s] = 0;
+	bool flag = false;
+	for (lo i = 1; i <= n; i++) {
+		flag = false;
+		for (lo j = 0; j < edge.size(); j++) {
+			u = edge[j].u, v = edge[j].v, w = edge[j].w;
+			if (dis[u] == INF) continue;
+			if (dis[v] > dis[u] + w) {
+				dis[v] = dis[u] + w;
+				flag = true;
+			}
+		}
+		if (!flag) {
+			break;
+		}
+	}
+	return flag;
+}
+
+signed main()
+{
+	cin >> t;
+	while (t--) {
+		edge.clear();
+		cin >> n >> m;
+		for (lo i = 1; i <= m; i++) {
+			cin >> c >> p >> W;
+			edge.push_back({c, p, W});
+			if (W >= 0) edge.push_back({p, c, W});
+		}
+		if (bellmanford(n, 1)) {
+			cout << "YES" << endl;
+		} else {
+			cout << "NO" << endl;
+		}
+	}
+}