'commit'

TangDou/AcWing/ErFenTu/POJ2594.cpp

@@ -0,0 +1,52 @@
+#include <iostream>
+#include <cstring>
+#include <algorithm>
+
+using namespace std;
+const int N = 510;
+int n, m;
+int g[N][N];
+
+// 匈牙利
+int match[N], st[N];
+int dfs(int u) {
+    for (int i = 1; i <= n; i++)
+        if (g[u][i] && !st[i]) {
+            st[i] = 1;
+            if (match[i] == -1 | dfs(match[i])) {
+                match[i] = u;
+                return 1;
+            }
+        }
+    return 0;
+}
+
+int main() {
+#ifndef ONLINE_JUDGE
+    freopen("POJ2594.in", "r", stdin);
+#endif
+    while (scanf("%d%d", &n, &m) && (n + m)) {
+        memset(g, 0, sizeof g);
+        while (m--) {
+            int x, y;
+            scanf("%d%d", &x, &y);
+            g[x][y] = 1;
+        }
+
+        // Floyd传递闭包
+        for (int k = 1; k <= n; ++k)
+            for (int i = 1; i <= n; ++i)
+                for (int j = 1; j <= n; ++j)
+                    g[i][j] |= g[i][k] & g[k][j];
+
+        int res = 0;
+        memset(match, -1, sizeof match);
+        for (int i = 1; i <= n; i++) {
+            memset(st, 0, sizeof st);
+            if (dfs(i)) res++;
+        }
+
+        printf("%d\n", n - res);
+    }
+    return 0;
+}