#2086. 【洛谷P3386】【模板】二分图最大匹配

https://sjzezoj.com/submission/73658

S2OJ/2086/2086.cpp

@@ -0,0 +1,115 @@
+#include <iostream>
+#include <algorithm>
+#include <iterator>
+#include <queue>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 505,
+          M = 5e4 + 5;
+const int INF = 0x3f3f3f3f;
+
+int n, m, e, s, t;
+int idx, head[N << 1], ver[M << 2], edge[M << 2], next[M << 2];
+int d[N << 1], cur[N << 1];
+
+void add(int u, int v, int w) {
+    ver[idx] = v;
+    edge[idx] = w;
+    next[idx] = head[u];
+    head[u] = idx++;
+}
+
+bool bfs() {
+    std::fill(std::begin(d), std::end(d), 0);
+
+    std::queue<int> q;
+
+    q.emplace(s);
+    d[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 (!d[v] && w) {
+                d[v] = d[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 (d[v] == d[u] + 1 && w) {
+            int k = dinic(v, std::min(limit - flow, w));
+
+            if (!k) d[v] = 0;
+
+            flow += k;
+            edge[i] -= k;
+            edge[i ^ 1] += 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 >> e;
+
+    s = 0, t = n + m + 1;
+
+    for (int i = 1; i <= n; i++) {
+        add(s, i, 1);
+        add(i, s, 0);
+    }
+
+    for (int i = 1; i <= m; i++) {
+        add(n + i, t, 1);
+        add(t, n + i, 0);
+    }
+
+    for (int i = 1, u, v; i <= e; i++) {
+        cin >> u >> v;
+
+        add(u, v + n, 1);
+        add(v + n, u, 0);
+    }
+
+    int res = 0;
+
+    while (bfs()) {
+        while (int flow = dinic(s, INF)) res += flow;
+    }
+
+    cout << res << endl;
+
+    return 0;
+}