#1547. 【2022 正睿 NOIP 十连测 Day3】点

https://sjzezoj.com/submission/63024

S2OJ/1547/1547.cpp

@@ -0,0 +1,85 @@
+#include <iostream>
+#include <algorithm>
+#include <cmath>
+#include <functional>
+#include <limits>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 5e5 + 5;
+const long long INF = 1e18;
+
+int n, m, w[N];
+long long f[N][2];
+std::vector<int> g[N];
+
+void dfs(int u, int fa) {
+    int k = g[u].size() / 2 + 1;
+    long long res = 0;
+    std::vector<long long> a;
+
+    for (int v : g[u]) {
+        if (v == fa) continue;
+
+        dfs(v, u);
+
+        if (w[v] <= w[u]) {
+            a.emplace_back(std::max(f[v][0] + w[v], f[v][1] + w[u]) - f[v][1] - m);
+            res += f[v][1] + m;
+        } else {
+            a.emplace_back(f[v][0] + w[u] - std::max(f[v][0] + w[v], f[v][1] + m));
+            res += std::max(f[v][0] + w[v], f[v][1] + m);
+        }
+    }
+
+    std::sort(a.begin(), a.end(), std::greater<>());
+
+    if (k - 1 > a.size()) {
+        f[u][0] = -INF;
+    } else {
+        long long sum = res;
+
+        for (int i = 0; i < k - 1; i++) sum += a[i];
+        for (int i = k - 1; i < a.size(); i++) sum += std::max(0ll, a[i]);
+
+        f[u][0] = sum;
+    }
+
+    if (k > a.size()) {
+        f[u][1] = -INF;
+    } else {
+        long long sum = res;
+
+        for (int i = 0; i < k; i++) sum += a[i];
+        for (int i = k; i < a.size(); i++) sum += std::max(0ll, a[i]);
+
+        f[u][1] = sum;
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> w[i];
+    }
+
+    for (int i = 1, u, v; i < n; i++) {
+        cin >> u >> v;
+
+        g[u].emplace_back(v);
+        g[v].emplace_back(u);
+    }
+
+    dfs(1, 1);
+
+    cout << f[1][1] << endl;
+
+    return 0;
+}