P2419 [USACO08JAN]Cow Contest S

R53034385

Luogu/problem/P2419/P2419.cpp

@@ -0,0 +1,40 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int n, m, a, b, f[105][105], ans[105];
+
+int main() {
+    cin >> n >> m;
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= n; j++) {
+            f[i][j] = i == j ? 0 : 0x3f3f3f3f;
+        }
+    }
+    for (int i = 1; i <= m; i++) {
+        cin >> a >> b;
+        f[a][b] = 1;
+    }
+    for (int k = 1; k <= n; k++) {
+        for (int i = 1; i <= n; i++) {
+            for (int j = 1; j <= n; j++) {
+                f[i][j] = min(f[i][j], f[i][k] + f[k][j]);
+            }
+        }
+    }
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= n; j++) {
+            if (f[i][j] != 0x3f3f3f3f && f[i][j] > 0) {
+                ans[i]++;
+                ans[j]++;
+            }
+        }
+    }
+    for (int i = 1; i <= n; i++) {
+        if (ans[i] == n - 1) {
+            ans[0]++;
+        }
+    }
+    cout << ans[0] << endl;
+    return 0;
+}