nyoj Cow Contest (传递闭包)

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<string>
#include<queue>
#include<algorithm>
#include<map>
#include<iomanip>
#include<climits>
#include<cmath>
#include<stdlib.h>
#include<vector>
#include<stack>
#include<set>
#define INF 2000000000
#define MAXN 110
#define maxn 1000010
#define Mod 1000007
#define N 1010
using namespace std;
typedef long long LL;

int n, m;
bool G[MAXN][MAXN];
int u, v;

void Floyd()
{
    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 main()
{
    while (~scanf("%d%d", &n, &m), n + m) {
        memset(G,0,sizeof(G));
        for (int i = 0; i < m; ++i) {
            scanf("%d%d", &u, &v);
            G[u][v] = true;
        }
        Floyd();
        int sum,ans = 0;
        for (int i = 1; i <= n; ++i) {
            sum = 0;
            for (int j = 1; j <= n; ++j) {
                if (G[i][j] || G[j][i]) sum++;
            }
            if (sum == n - 1) ans++;
        }
        cout << ans << endl;
    }
    return 0;
}