#1788. 【2017.3长乐省选集训Day8T3】修路

https://sjzezoj.com/submission/65457

S2OJ/1788/1788.cpp

@@ -0,0 +1,105 @@
+#include <iostream>
+#include <cstring>
+#include <queue>
+#include <utility>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e4 + 5,
+          K = 11;
+const int INF = 0x3f3f3f3f;
+
+int n, m, d, f[1 << K][N], f1[1 << K];
+std::vector<std::pair<int, int>> g[N];
+
+int steiner(int s) {
+    int k = 0;
+
+    memset(f, 0x3f, sizeof(f));
+
+    for (int i = 1; i <= d; i++) {
+        std::queue<int> q;
+
+        if (s & (1 << (i - 1))) {
+            f[1 << k++][i] = 0;
+            f[1 << k++][n - i + 1] = 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;
+                    }
+                }
+            }
+        }
+    }
+
+    int res = INF;
+
+    for (int i = 1; i <= n; i++) {
+        res = std::min(res, f[(1 << k) - 1][i]);
+    }
+
+    return res;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m >> d;
+
+    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(f1, 0x3f, sizeof(f1));
+
+    f1[0] = 0;
+
+    for (int s = 1; s < 1 << d; s++) {
+        for (int t = s; t; t = (t - 1) & s) {
+            f1[s] = std::min(f1[s], f1[s ^ t] + steiner(t));
+        }
+    }
+
+    cout << (f1[(1 << d) - 1] == INF ? -1 : f1[(1 << d) - 1]) << endl;
+
+    return 0;
+}