P1342 请柬

R53781989

Luogu/problem/P1342/P1342.cpp

@@ -0,0 +1,63 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int n, m, u, v;
+long long w, dist1[100005], dist2[100005], ans;
+vector<pair<int, long long>> g1[100005], g2[100005];
+bool st1[100005], st2[100005];
+
+void dijkstra1() {
+    memset(dist1, 0x3f, sizeof(dist1));
+    dist1[1] = 0;
+    priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> q;
+    q.push(make_pair(0, 1));
+    while (!q.empty()) {
+        auto t = q.top();
+        q.pop();
+        if (st1[t.second]) continue;
+        for (auto i : g1[t.second]) {
+            if (dist1[i.first] > t.first + i.second) {
+                dist1[i.first] = t.first + i.second;
+                q.push(make_pair(dist1[i.first], i.first));
+            }
+        }
+        st1[t.second] = true;
+    }
+}
+
+void dijkstra2() {
+    memset(dist2, 0x3f, sizeof(dist2));
+    dist2[1] = 0;
+    priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> q;
+    q.push(make_pair(0, 1));
+    while (!q.empty()) {
+        auto t = q.top();
+        q.pop();
+        if (st2[t.second]) continue;
+        for (auto i : g2[t.second]) {
+            if (dist2[i.first] > t.first + i.second) {
+                dist2[i.first] = t.first + i.second;
+                q.push(make_pair(dist2[i.first], i.first));
+            }
+        }
+        st2[t.second] = true;
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin >> n >> m;
+    for (int i = 1; i <= m; i++) {
+        cin >> u >> v >> w;
+        g1[u].push_back(make_pair(v, w));
+        g2[v].push_back(make_pair(u, w));
+    }
+    dijkstra1();
+    dijkstra2();
+    for (int i = 2; i <= n; i++) {
+        ans += dist1[i] + dist2[i];
+    }
+    cout << ans << endl;
+    return 0;
+}