P2458 [SDOI2006]保安站岗

https://www.luogu.com.cn/record/86522118

Luogu/P2458/P2458.cpp

@@ -0,0 +1,59 @@
+#include <iostream>
+#include <algorithm>
+#include <compare>
+#include <limits>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1505;
+
+int n, a[N], f[N][3];
+std::vector<int> g[N];
+
+void dfs(int u, int fa) {
+    f[u][2] = a[u];
+
+    for (int v : g[u]) {
+        if (v == fa) continue;
+
+        dfs(v, u);
+
+        f[u][0] += std::min(f[v][1], f[v][2]);
+        f[u][2] += std::min({f[v][0], f[v][1], f[v][2]});
+    }
+
+    f[u][1] = std::numeric_limits<int>::max();
+
+    for (int v : g[u]) {
+        if (v == fa) continue;
+
+        f[u][1] = std::min(f[u][1], f[u][0] - std::min(f[v][1], f[v][2]) + f[v][2]);
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+
+    for (int i = 1, u, v, m; i <= n; i++) {
+        cin >> u >> a[u] >> m;
+
+        while (m--) {
+            cin >> v;
+
+            g[u].emplace_back(v);
+            g[v].emplace_back(u);
+        }
+    }
+
+    dfs(1, 0);
+
+    cout << std::min(f[1][1], f[1][2]) << endl;
+
+    return 0;
+}