new file: P1352.cpp

P1352.cpp

@@ -0,0 +1,48 @@
+#include <bits/stdc++.h>
+#define int long long
+using namespace std;
+int n;
+int r[10000];
+int fa[10000];
+int f[10000][2];
+vector<int> chi[10000];
+int dp(int now, bool choose) // 现在到哪个节点且父亲是否取
+{
+    if (f[now][choose])
+        return f[now][choose];
+    if (choose)
+    {
+        int ans = 0;
+        for (auto k : chi[now])
+        {
+            ans += dp(k, 0);
+        }
+        f[now][choose] = ans;
+        return ans;
+    }
+    int ans1 = 0, ans2 = 0;
+    for (auto k : chi[now])
+        ans1 += dp(k, 0);
+    for (auto k : chi[now])
+        ans2 += dp(k, 1);
+    f[now][choose] = max(ans1, ans2 + r[now]);
+    return f[now][choose];
+}
+signed main()
+{
+    scanf("%lld", &n);
+    for (int i = 1; i <= n; ++i)
+        scanf("%lld", &r[i]);
+    for (int i = 1; i < n; ++i)
+    {
+        int u, v;
+        scanf("%lld%lld", &u, &v);
+        fa[u] = v;
+        chi[v].push_back(u);
+    }
+    int root = 1;
+    while (fa[root])
+        root = fa[root];
+    printf("%lld\n", dp(root, 0));
+    return 0;
+}