POJ 3660 Cow Contest——flody求传递闭包

题意：有n个牛， 他们之间有m个优劣关系， 求有多少个牛的优劣关系完全确定

思路：求出传递闭包后判断每个牛是否和其他所有牛都有关系，是的话ans++

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
const int maxn = 110;
int n, m, d[maxn][maxn];
int main() {
while(~scanf("%d %d", &n, &m)) {
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
d[i][j] = 0;
}
}
while (m--) {
int a, b; scanf("%d %d", &a, &b);
d[a][b] = 1;
}
for (int k = 1; k <= n; k++) {
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
d[i][j] = d[i][j] || (d[i][k] && d[k][j]);
}
}
}
int ans = 0;
for (int i = 1; i <= n; i++) {
bool ok = true;
for (int j = 1; j <= n; j++) {
if (i != j && !d[i][j] && !d[j][i]) { ok = false; break; }
}
if (ok) ans++;
}
printf("%d\n", ans);
}
}