nyoj-211-Cow Contest(floyd算法)

题目链接

/*
    Name:nyoj-211-Cow Contest
    Copyright:
    Author:
    Date: 2018/4/27 21:02:06
    Description:
    floyd算法
    大佬的惊奇思路 
*/
#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

const int MAXN = 105;
const int INF = 0x3f3f3f3f;
int N, g[MAXN][MAXN], M;

void floyd() {
    for (int k=1; k<=N; k++) {
        for (int i=1; i<=N; i++) {
            for (int j=1; j<=N; j++) {
                if (g[i][k] && g[k][j])
                    g[i][j] = 1;//有关系 
            }
        }
    }
}
int main()
{
    while (cin>>N>>M, N+M) {
        memset(g, 0, sizeof(g));
        for (int i=0; i<M; i++) {
            int x, y;
            cin>>x>>y;
            g[x][y] = 1;
        }
        floyd();
        int i, j, ans=0;
        for (i=1; i<=N; i++) {
            for (j=1; j<=N; j++) {
                if (i==j) continue;
                if (g[i][j] == 0 && g[j][i] == 0) break;//和其他牛中的一头没有关系就不能确定排名 
            }
            if (j > N) ans++;
        }
        cout<<ans<<endl;
    }
    return 0;
}