Initial commit: C++ courseware

2.Course/2.深入浅出程序设计竞赛（提高篇）/最短路/C++源码/04b_difference_constraints.cpp

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+// P5960：求任意一组差分约束可行解。C++11。
+#include <iostream>
+#include <vector>
+#include <queue>
+using namespace std;
+using ll = long long;
+struct Edge { int v, w; };
+
+bool solve(const vector<vector<Edge>>& g, vector<ll>& dis) {
+    int n = static_cast<int>(g.size()) - 1;
+    dis.assign(n + 1, 0);
+    vector<int> len(n + 1, 0);
+    vector<bool> inq(n + 1, true);
+    queue<int> q;
+    for (int i = 1; i <= n; ++i) q.push(i);
+    while (!q.empty()) {
+        int u = q.front(); q.pop();
+        inq[u] = false;
+        for (auto e : g[u]) {
+            int v = e.v;
+            ll nd = dis[u] + e.w;
+            if (nd >= dis[v]) continue;
+            dis[v] = nd;
+            len[v] = len[u] + 1;
+            if (len[v] >= n) return false;
+            if (!inq[v]) {
+                q.push(v); inq[v] = true;
+            }
+        }
+    }
+    return true;
+}
+
+int main() {
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+    int n, m;
+    if (!(cin >> n >> m)) return 0;
+    vector<vector<Edge>> g(n + 1);
+    for (int i = 0; i < m; ++i) {
+        int a, b, w; cin >> a >> b >> w;
+        g[b].push_back({a, w});
+    }
+    vector<ll> dis;
+    if (!solve(g, dis)) cout << "NO\n";
+    else {
+        for (int i = 1; i <= n; ++i)
+            cout << dis[i] << (i == n ? '\n' : ' ');
+    }
+}