P5960 【模板】差分约束算法

https://www.luogu.com.cn/record/94859058

Luogu/P5960/P5960.cpp

@@ -0,0 +1,74 @@
+#include <iostream>
+#include <algorithm>
+#include <queue>
+#include <utility>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 5005;
+const int INF = 0x3f3f3f3f;
+
+int n, m, dist[N], cnt[N];
+std::vector<std::pair<int, int>> g[N];
+
+bool spfa() {
+    std::fill_n(dist, N, INF);
+
+    std::queue<int> q;
+
+    q.emplace(0);
+    dist[0] = 0;
+
+    while (!q.empty()) {
+        int u = q.front();
+        q.pop();
+
+        for (auto e : g[u]) {
+            int v = e.first,
+                w = e.second;
+
+            if (dist[v] > dist[u] + w) {
+                dist[v] = dist[u] + w;
+                cnt[v] = cnt[u] + 1;
+
+                if (cnt[v] > n) return false;
+
+                q.emplace(v);
+            }
+        }
+    }
+
+    return true;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m;
+
+    for (int i = 1, u, v, w; i <= m; i++) {
+        cin >> u >> v >> w;
+
+        g[v].emplace_back(u, w);
+    }
+
+    for (int i = 1; i <= n; i++) {
+        g[0].emplace_back(i, 0);
+    }
+
+    if (spfa()) {
+        for (int i = 1; i <= n; i++) {
+            cout << dist[i] << ' ';
+        }
+
+        cout << endl;
+    } else {
+        cout << "NO" << endl;
+    }
+
+    return 0;
+}