904. 虫洞

https://www.acwing.com/problem/content/submission/code_detail/7892844/

AcWing/904/904.cpp

@@ -0,0 +1,56 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int f, n, m, w, u, v, t, dist[505], cnt[505];
+vector<pair<int, int>> g[505];
+bool vis[505];
+
+bool spfa() {
+    memset(dist, 0x3f, sizeof(dist));
+    memset(vis, 0x00, sizeof(vis));
+    memset(cnt, 0x00, sizeof(cnt));
+    queue<int> q;
+    for (int i = 1; i <= n; i++) {
+        q.push(i);
+        vis[i] = true;
+    }
+    while (!q.empty()) {
+        int t = q.front();
+        q.pop();
+        vis[t] = false;
+        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;
+                if (!vis[i.first]) {
+                    q.push(i.first);
+                    vis[i.first] = true;
+                }
+            }
+        }
+    }
+    return false;
+}
+
+int main() {
+    cin >> f;
+    while (f--) {
+        cin >> n >> m >> w;
+        for (int i = 1; i <= n; i++) {
+            g[i].clear();
+        }
+        for (int i = 1; i <= m; i++) {
+            cin >> u >> v >> t;
+            g[u].push_back(make_pair(v, t));
+            g[v].push_back(make_pair(u, t));
+        }
+        for (int i = 1; i <= w; i++) {
+            cin >> u >> v >> t;
+            g[u].push_back(make_pair(v, -t));
+        }
+        cout << (spfa() ? "YES" : "NO") << endl;
+    }
+    return 0;
+}