P1231 教辅的组成

R71699895

Luogu/P1231/P1231.cpp

@@ -0,0 +1,110 @@
+#include <cstring>
+#include <iostream>
+#include <queue>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 100005,
+          M = 1000005;
+
+int n, f, d, m, flow, ans;
+
+// Graph
+int idx, head[N], edge[M << 1], ver[M << 1], next[M << 1];
+
+void add(int u, int v, int w) {
+    next[idx] = head[u];
+    ver[idx] = v;
+    edge[idx] = w;
+    head[u] = idx++;
+}
+
+// Dinic
+int dist[N], cur[N];
+
+bool bfs() {
+    memset(dist, 0x00, sizeof(dist));
+    std::queue<int> q;
+    q.push(0);
+    dist[0] = 1;
+    cur[0] = head[0];
+
+    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 (w && !dist[v]) {
+                dist[v] = dist[u] + 1;
+                cur[v] = head[v];
+                if (v == n) return true;
+                q.push(v);
+            }
+        }
+    }
+    return false;
+}
+
+int dinic(int u, int limit) {
+    if (u == n) return limit;
+
+    int flow = 0;
+    for (int &i = cur[u]; ~i && flow < limit; i = next[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);
+    memset(head, 0xff, sizeof(head));
+    cin >> n >> f >> d;
+    for (int i = 1; i <= f; i++) {
+        add(0, i, 1);
+        add(i, 0, 0);
+    }
+    cin >> m;
+    for (int i = 1; i <= m; i++) {
+        int x, y;
+        cin >> x >> y;
+        add(y, f + d + x, 1);
+        add(f + d + x, y, 0);
+    }
+
+    for (int i = 1; i <= n; i++) {
+        add(f + d + i, f + d + n + i, 1);
+        add(f + d + n + i, f + d + i, 0);
+    }
+
+    cin >> m;
+    for (int i = 1; i <= m; i++) {
+        int x, y;
+        cin >> x >> y;
+        add(f + d + n + x, f + y, 1);
+        add(f + y, f + d + n + x, 0);
+    }
+
+    n = f + d + n * 2 + 1;
+    for (int i = 1; i <= d; i++) {
+        add(f + i, n, 1);
+        add(n, f + i, 0);
+    }
+
+    while (bfs()) {
+        while (flow = dinic(0, 0x3f3f3f3f)) ans += flow;
+    }
+    cout << ans << endl;
+    return 0;
+}