#1422. Floodfill

https://sjzezoj.com/submission/66820

S2OJ/1422/1422.cpp

@@ -0,0 +1,226 @@
+#include <iostream>
+#include <algorithm>
+#include <iterator>
+#include <numeric>
+#include <queue>
+#include <unordered_set>
+#include <utility>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 105,
+          M = N * N * 2;
+const int INF = 0x3f3f3f3f;
+
+const int d[][2]{{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
+
+struct DSU : private std::vector<int> {
+    DSU(const int& _n)
+        : std::vector<int>(_n + 1) {
+        std::iota(begin(), end(), 0);
+    }
+
+    int find(const int& x) {
+        return x == at(x) ? x : at(x) = find(at(x));
+    }
+
+    bool check(const int& x, const int& y) {
+        return find(x) == find(y);
+    }
+
+    void merge(int x, int y) {
+        x = find(x);
+        y = find(y);
+
+        if (x != y) at(y) = x;
+    }
+};
+
+int n, m, s, t, cnt, a[N * N], b[N * N], c[N * N];
+int idx, head[N * N], ver[M], edge[M], next[M];
+int cur[N * N], dist[N * N];
+bool g1[N][N], g2[N][N], vis[N][N], color[N * N];
+std::unordered_set<int> g[N * N];
+
+int id(int x, int y) {
+    return (x - 1) * m + y;
+}
+
+void add(int u, int v, int w) {
+    next[idx] = head[u];
+    ver[idx] = v;
+    edge[idx] = w;
+    head[u] = idx++;
+}
+
+bool bfs() {
+    std::fill(std::begin(dist), std::end(dist), 0);
+
+    std::queue<int> q;
+
+    q.emplace(s);
+    dist[s] = 1;
+    cur[s] = head[s];
+
+    while (!q.empty()) {
+        int u = q.front();
+        q.pop();
+
+        for (int i = head[u]; ~i; i = next[i]) {
+            int v = ver[i],
+                w = edge[i];
+
+            if (!dist[v] && w) {
+                dist[v] = dist[u] + 1;
+                cur[v] = head[v];
+
+                if (v == t) return true;
+
+                q.emplace(v);
+            }
+        }
+    }
+
+    return false;
+}
+
+int dinic(int u, int limit) {
+    if (u == t) return limit;
+
+    int flow = 0;
+
+    for (int i = cur[u]; ~i && flow < limit; i = next[i]) {
+        cur[u] = i;
+
+        int v = ver[i],
+            w = edge[i];
+
+        if (dist[v] == dist[u] + 1 && w) {
+            int k = dinic(v, std::min(w, limit - flow));
+
+            if (!k) dist[v] = 0;
+
+            edge[i] -= k;
+            edge[i ^ 1] += k;
+            flow += k;
+        }
+    }
+
+    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;
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= m; j++) {
+            char c;
+
+            cin >> c;
+
+            g1[i][j] = c - '0';
+        }
+    }
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= m; j++) {
+            char c;
+
+            cin >> c;
+
+            g2[i][j] = c - '0';
+        }
+    }
+
+    DSU dsu(n * m);
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= m; j++) {
+            if (vis[i][j]) continue;
+
+            std::queue<std::pair<int, int>> q;
+
+            q.emplace(i, j);
+            color[c[id(i, j)] = ++cnt] = g1[i][j];
+            vis[i][j] = true;
+
+            while (!q.empty()) {
+                int x = q.front().first,
+                    y = q.front().second;
+                q.pop();
+
+                if (g1[i][j] != g2[x][y]) a[cnt]++;
+                else b[cnt]++;
+
+                for (auto d : d) {
+                    int xx = x + d[0],
+                        yy = y + d[1];
+
+                    if (xx < 1 || xx > n || yy < 1 || yy > m || g1[x][y] != g1[xx][yy] || vis[xx][yy]) continue;
+
+                    q.emplace(xx, yy);
+                    vis[xx][yy] = true;
+                    dsu.merge(id(i, j), id(xx, yy));
+                }
+            }
+        }
+    }
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= m; j++) {
+            for (auto d : d) {
+                int xx = i + d[0],
+                    yy = j + d[1];
+
+                if (xx < 1 || xx > n || yy < 1 || yy > m || g1[i][j] == g1[xx][yy]) continue;
+
+                int u = c[dsu.find(id(i, j))],
+                    v = c[dsu.find(id(xx, yy))];
+
+                g[u].emplace(v);
+                g[v].emplace(u);
+            }
+        }
+    }
+
+    s = 0, t = cnt + 1;
+
+    for (int i = 1; i <= cnt; i++) {
+        if (color[i] == 0) {
+            add(s, i, a[i]);
+            add(i, s, 0);
+
+            add(i, t, b[i]);
+            add(t, i, 0);
+
+            for (int v : g[i]) {
+                add(i, v, INF);
+                add(v, i, 0);
+            }
+        } else {
+            add(s, i, b[i]);
+            add(i, s, 0);
+
+            add(i, t, a[i]);
+            add(t, i, 0);
+        }
+    }
+
+    int res = 0;
+
+    while (bfs()) {
+        while (int flow = dinic(s, INF)) res += flow;
+    }
+
+    cout << res << endl;
+
+    return 0;
+}