P1642 规划

https://www.luogu.com.cn/record/86538400

Luogu/P1642/P1642.cpp

@@ -0,0 +1,99 @@
+#include <iostream>
+#include <algorithm>
+#include <array>
+#include <iomanip>
+#include <limits>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 105;
+const double eps = 1e-4;
+
+int n, m;
+std::array<int, N> siz;
+std::array<double, N> d;
+std::array<std::array<double, N>, N> f;
+std::array<std::vector<int>, N> g;
+std::array<std::pair<int, int>, N> a;
+
+void dfs(int u, int fa) {
+    f[u][0] = 0;
+    siz[u] = 1;
+
+    for (int v : g[u]) {
+        if (v == fa) continue;
+
+        dfs(v, u);
+
+        siz[u] += siz[v];
+
+        for (int i = std::min(siz[u], m); ~i; i--) {
+            for (int j = 0; j <= std::min(siz[v], i); j++) {
+                f[u][i] = std::max(f[u][i], f[u][i - j] + f[v][j]);
+            }
+        }
+    }
+
+    for (int i = std::min(m, siz[u]); i; i--) {
+        f[u][i] = f[u][i - 1] + d[u];
+    }
+}
+
+bool check(double mid) {
+    for (int i = 1; i <= n; i++) {
+        d[i] = static_cast<double>(a[i].first) - mid * a[i].second;
+    }
+
+    std::for_each(f.begin(), f.end(), [&](auto &x) {
+        std::fill(x.begin(), x.end(), std::numeric_limits<int>::min());
+    });
+
+    dfs(1, -1);
+
+    for (int i = 1; i <= n; i++) {
+        if (f[i][m] > -eps) return true;
+    }
+
+    return false;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m;
+
+    m = n - m;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i].first;
+    }
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i].second;
+    }
+
+    for (int i = 1, u, v; i < n; i++) {
+        cin >> u >> v;
+
+        g[u].emplace_back(v);
+        g[v].emplace_back(u);
+    }
+
+    double l = 0,
+           r = 10000;
+
+    while (r - l > eps) {
+        double mid = (l + r) / 2;
+
+        if (check(mid)) l = mid;
+        else r = mid;
+    }
+
+    cout << std::fixed << std::setprecision(1) << l << endl;
+
+    return 0;
+}