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/03b_postman.cpp

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+// P1629 / 教材例 10-3：有向正权图，题目保证任意两点互相可达。
+// 输入 n m，随后 m 行 u v w；顶点从 1 编号。
+#include <iostream>
+#include <vector>
+#include <queue>
+#include <utility>
+#include <functional>
+using namespace std;
+using ll = long long;
+using State = pair<ll, int>;
+struct Edge { int to; ll w; };
+vector<ll> dijkstra(const vector<vector<Edge>> &g, int s) {
+    const ll INF = (1LL << 60);
+    vector<ll> dis(g.size(), INF);
+    priority_queue<State, vector<State>, greater<State>> q;
+    dis[s] = 0; q.push({0, s});
+    while (!q.empty()) {
+        State cur = q.top(); q.pop();
+        ll d = cur.first; int u = cur.second;
+        if (d != dis[u]) continue;
+        for (const auto &e : g[u]) {
+            ll nd = d + e.w;
+            if (nd < dis[e.to]) {
+                dis[e.to] = nd;
+                q.push({nd, e.to});
+            }
+        }
+    }
+    return dis;
+}
+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), rg(n + 1);
+    for (int i = 0; i < m; ++i) {
+        int u, v; ll w; cin >> u >> v >> w;
+        g[u].push_back({v, w});
+        rg[v].push_back({u, w});
+    }
+    vector<ll> out = dijkstra(g, 1);
+    vector<ll> back = dijkstra(rg, 1);
+    ll ans = 0;
+    for (int i = 2; i <= n; ++i) ans += out[i] + back[i];
+    cout << ans << '\n';
+}