3232. 圈地游戏

https://hydro.ac/d/bzoj/record/63b7bef8eae63550a15bee05

BZOJ/3232/3232.cpp

@@ -0,0 +1,112 @@
+#include <iostream>
+#include <algorithm>
+#include <iomanip>
+#include <iterator>
+#include <queue>
+#include <tuple>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 55;
+const double eps = 1e-6;
+
+int n, m, s[N][N];
+std::vector<std::tuple<int, int, int>> g[N * N];
+int cnt[N * N];
+double dist[N * N];
+bool vis[N * N];
+
+int id(int x, int y) {
+    return (x - 1) * (m + 1) + y;
+}
+
+bool check(double x) {
+    std::fill(std::begin(cnt), std::end(cnt), 0);
+    std::fill(std::begin(dist), std::end(dist), -1e9);
+    std::fill(std::begin(vis), std::end(vis), false);
+
+    std::queue<int> q;
+
+    q.emplace(1);
+    dist[1] = 0;
+    vis[1] = true;
+
+    while (!q.empty()) {
+        int u = q.front();
+        q.pop();
+
+        vis[u] = false;
+
+        for (auto e : g[u]) {
+            int v, a, b;
+
+            std::tie(v, a, b) = e;
+
+            double w = static_cast<double>(b) - x * a;
+
+            if (dist[v] < dist[u] + w) {
+                dist[v] = dist[u] + w;
+
+                if (!vis[v]) {
+                    cnt[v] = cnt[u] + 1;
+
+                    if (cnt[v] > (n + 1) * (m + 1)) return false;
+
+                    vis[v] = true;
+                    q.emplace(v);
+                }
+            }
+        }
+    }
+
+    return true;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m;
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1, x; j <= m; j++) {
+            cin >> x;
+
+            s[i][j] = s[i][j - 1] + x;
+        }
+    }
+
+    for (int i = 1; i <= n + 1; i++) {
+        for (int j = 1, x; j <= m; j++) {
+            cin >> x;
+
+            g[id(i, j)].emplace_back(id(i, j + 1), x, 0);
+            g[id(i, j + 1)].emplace_back(id(i, j), x, 0);
+        }
+    }
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1, x; j <= m + 1; j++) {
+            cin >> x;
+
+            g[id(i, j)].emplace_back(id(i + 1, j), x, -s[i][j - 1]);
+            g[id(i + 1, j)].emplace_back(id(i, j), x, s[i][j - 1]);
+        }
+    }
+
+    double l = 0, r = 1000;
+
+    while (r - l > eps) {
+        double mid = (l + r) / 2;
+
+        if (check(mid)) r = mid;
+        else l = mid;
+    }
+
+    cout << std::fixed << std::setprecision(3) << l << endl;
+
+    return 0;
+}