2668. [cqoi2012] 交换棋子

https://hydro.ac/d/bzoj/record/63bebe955b6d7fa6ab4b04d3

BZOJ/2668/2668.cpp

@@ -0,0 +1,189 @@
+#include <iostream>
+#include <algorithm>
+#include <iterator>
+#include <queue>
+#include <utility>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 25,
+          M = N * N * 8;
+const int INF = 0x3f3f3f3f;
+
+const int d[][2] = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}, {-1, 1}, {1, 1}, {1, -1}, {-1, -1}};
+
+int n, m, s, t, cnt, cnt1, cnt2, cost;
+bool g1[N][N], g2[N][N];
+int idx, head[M], ver[M << 1], next[M << 1];
+std::pair<int, int> edge[M << 1];
+int dist[M];
+bool vis[M];
+
+int id(int x, int y, int k = 0) {
+    return n * m * k + (x - 1) * m + y;
+}
+
+void add(int u, int v, int c, int w) {
+    next[idx] = head[u];
+    ver[idx] = v;
+    edge[idx] = std::make_pair(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.push(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 && !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;
+
+    s = 0, t = id(n, m, 1) + 1;
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= m; j++) {
+            char c;
+
+            cin >> c;
+
+            if (c == '1') {
+                g1[i][j] = true;
+                cnt1++;
+            }
+        }
+    }
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= m; j++) {
+            char c;
+
+            cin >> c;
+
+            if (c == '1') {
+                g2[i][j] = true;
+                cnt2++;
+            }
+        }
+    }
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= m; j++) {
+            if (g1[i][j] && !g2[i][j]) {
+                add(s, id(i, j), 1, 0);
+                add(id(i, j), s, 0, 0);
+                cnt++;
+            } else if (!g1[i][j] && g2[i][j]) {
+                add(id(i, j, 1), t, 1, 0);
+                add(t, id(i, j, 1), 0, 0);
+            }
+        }
+    }
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= m; j++) {
+            char c;
+
+            cin >> c;
+
+            int x = c - '0';
+
+            add(id(i, j), id(i, j, 1), x >> 1, 0);
+            add(id(i, j, 1), id(i, j), 0, 0);
+
+            if (g1[i][j] != g2[i][j] && x % 2 == 1) {
+                add(id(i, j), id(i, j, 1), 1, 0);
+                add(id(i, j, 1), id(i, j), 0, 0);
+            }
+
+            for (auto d : d) {
+                int xx = i + d[0],
+                    yy = j + d[1];
+
+                if (xx < 1 || xx > n || yy < 1 || yy > m) continue;
+
+                add(id(i, j, 1), id(xx, yy), INF, 1);
+                add(id(xx, yy), id(i, j, 1), 0, -1);
+            }
+        }
+    }
+
+    int res = 0;
+
+    while (spfa()) {
+        while (int flow = dinic(s, INF)) res += flow;
+    }
+
+    if (cnt1 != cnt2 || res < cnt) {
+        cout << -1 << endl;
+    } else {
+        cout << cost << endl;
+    }
+
+    return 0;
+}