#187. 最小斯坦纳树

https://loj.ac/s/1714072

LibreOJ/187/187.cpp

@@ -0,0 +1,84 @@
+#include <iostream>
+#include <cstring>
+#include <queue>
+#include <utility>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 105,
+          K = 12;
+const int INF = 0x3f3f3f3f;
+
+int n, m, k, a[K], f[1 << K][N], ans = INF;
+std::vector<std::pair<int, int>> g[N];
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m >> k;
+
+    for (int i = 1, u, v, w; i <= m; i++) {
+        cin >> u >> v >> w;
+
+        g[u].emplace_back(v, w);
+        g[v].emplace_back(u, w);
+    }
+
+    memset(f, 0x3f, sizeof(f));
+
+    for (int i = 1; i <= k; i++) {
+        cin >> a[i];
+
+        f[1 << (i - 1)][a[i]] = 0;
+    }
+
+    for (int s = 0; s < 1 << k; s++) {
+        std::queue<int> q;
+        std::vector<bool> vis(n + 1);
+
+        for (int i = 1; i <= n; i++) {
+            for (int t = s & (s - 1); t; t = (t - 1) & s) {
+                f[s][i] = std::min(f[s][i], f[t][i] + f[s ^ t][i]);
+            }
+
+            if (f[s][i] != INF) {
+                q.emplace(i);
+                vis[i] = true;
+            }
+        }
+
+        // SPFA
+        while (!q.empty()) {
+            int u = q.front();
+            q.pop();
+
+            vis[u] = false;
+
+            for (auto e : g[u]) {
+                int v = e.first,
+                    w = e.second;
+
+                if (f[s][v] > f[s][u] + w) {
+                    f[s][v] = f[s][u] + w;
+
+                    if (!vis[v]) {
+                        q.emplace(v);
+                        vis[v] = true;
+                    }
+                }
+            }
+        }
+    }
+
+    for (int i = 1; i <= k; i++) {
+        ans = std::min(ans, f[(1 << k) - 1][a[i]]);
+    }
+
+    cout << ans << endl;
+
+    return 0;
+}