#366. 古代游戏记录(record)

https://sjzezoj.com/submission/66788

S2OJ/366/366.cpp

@@ -0,0 +1,158 @@
+#include <iostream>
+#include <algorithm>
+#include <iterator>
+#include <queue>
+#include <unordered_map>
+#include <utility>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 55,
+          M = N * N * 4;
+const int INF = 0x3f3f3f3f;
+
+const std::unordered_map<char, std::pair<int, int>> d{
+    {'L', {0, -1}},
+    {'R', {0, 1}},
+    {'U', {-1, 0}},
+    {'D', {1, 0}},
+};
+
+int n, m, k, s, t, cnt, id[N][N], cost;
+int idx, head[M], ver[M << 1], next[M << 1];
+std::pair<int, int> edge[M << 1];
+int dist[M];
+bool vis[M];
+
+void add(int u, int v, int c, int w) {
+    next[idx] = head[u];
+    ver[idx] = v;
+    edge[idx] = {c, w};
+    head[u] = idx++;
+}
+
+bool spfa() {
+    std::fill(std::begin(vis), std::end(vis), false);
+    std::fill(std::begin(dist), std::end(dist), INF);
+
+    std::queue<int> q;
+
+    q.emplace(s);
+    dist[s] = 0;
+    vis[s] = true;
+
+    while (!q.empty()) {
+        int u = q.front();
+        q.pop();
+
+        vis[u] = false;
+
+        for (int i = head[u]; ~i; i = next[i]) {
+            int v = ver[i],
+                c = edge[i].first,
+                w = edge[i].second;
+
+            if (c > 0 && dist[v] > dist[u] + w) {
+                dist[v] = dist[u] + w;
+
+                if (!vis[v]) {
+                    q.emplace(v);
+
+                    vis[v] = true;
+                }
+            }
+        }
+    }
+
+    return dist[t] != INF;
+}
+
+int dinic(int u, int limit) {
+    if (u == t) return limit;
+
+    int flow = 0;
+
+    vis[u] = true;
+
+    for (int i = head[u]; ~i && flow < limit; i = next[i]) {
+        int v = ver[i],
+            c = edge[i].first,
+            w = edge[i].second;
+
+        if (dist[v] == dist[u] + w && c > 0 && !vis[v]) {
+            int k = dinic(v, std::min(c, limit - flow));
+
+            if (!k) dist[v] = INF;
+
+            edge[i].first -= k;
+            edge[i ^ 1].first += k;
+            flow += k;
+            cost += k * w;
+        }
+    }
+
+    vis[u] = false;
+
+    return flow;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    std::fill(std::begin(head), std::end(head), -1);
+
+    cin >> n >> m >> k;
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= m; j++) {
+            id[i][j] = ++cnt;
+
+            add(s, id[i][j], 1, 0);
+            add(id[i][j], s, 0, 0);
+        }
+    }
+
+    for (int i = 1; i <= k; i++) {
+        int x, y;
+        char d;
+
+        cin >> x >> y >> d;
+
+        x++, y++;
+
+        int xx = x + ::d.at(d).first,
+            yy = y + ::d.at(d).second,
+            p = ++cnt;
+
+        add(id[xx][yy], p, 1, 0);
+        add(p, id[xx][yy], 0, 0);
+
+        id[xx][yy] = ++cnt;
+
+        add(p, id[xx][yy], 1, 0);
+        add(id[xx][yy], p, 0, 0);
+
+        add(id[x][y], p, 1, -1);
+        add(p, id[x][y], 0, 1);
+    }
+
+    t = ++cnt;
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= m; j++) {
+            add(id[i][j], t, 1, 0);
+            add(t, id[i][j], 0, 0);
+        }
+    }
+
+    while (spfa() && dist[t] < 0) {
+        while (dinic(s, INF)) {}
+    }
+
+    cout << k + cost << endl;
+
+    return 0;
+}