P2939 [USACO09FEB]Revamping Trails G

https://www.luogu.com.cn/record/75807146

Luogu/P2939/P2939.cpp

@@ -0,0 +1,74 @@
+#include <cstring>
+#include <iostream>
+#include <queue>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e4 + 5;
+
+int n, m, k, dist[N << 5];
+std::vector<std::pair<int, int>> g[N << 5];
+bool vis[N << 5];
+
+void dijkstra() {
+    memset(dist, 0x3f, sizeof(dist));
+
+    std::priority_queue<std::pair<int, int>, std::vector<std::pair<int, int>>, std::greater<std::pair<int, int>>> q;
+
+    q.push(std::make_pair(0, 1));
+    dist[1] = 0;
+
+    while (!q.empty()) {
+        auto t = q.top();
+        q.pop();
+
+        if (vis[t.second]) continue;
+
+        for (auto e : g[t.second]) {
+            int v = e.first,
+                w = e.second;
+
+            if (dist[v] > t.first + w) {
+                dist[v] = t.first + w;
+
+                q.push(std::make_pair(dist[v], v));
+            }
+        }
+
+        vis[t.second] = true;
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> n >> m >> k;
+
+    for (int i = 1, u, v, w; i <= m; i++) {
+        cin >> u >> v >> w;
+
+        g[u].push_back(std::make_pair(v, w));
+        g[v].push_back(std::make_pair(u, w));
+
+        for (int j = 1; j <= k; j++) {
+            g[u + (j - 1) * n].push_back(std::make_pair(v + j * n, 0));
+            g[v + (j - 1) * n].push_back(std::make_pair(u + j * n, 0));
+
+            g[u + j * n].push_back(std::make_pair(v + j * n, w));
+            g[v + j * n].push_back(std::make_pair(u + j * n, w));
+        }
+    }
+
+    for (int i = 0; i <= k; i++) {
+        g[i * n].push_back(std::make_pair(i * n + n, 0));
+    }
+
+    dijkstra();
+
+    cout << dist[n * k + n] << endl;
+
+    return 0;
+}