HDU 3357 Stock Chase

http://acm.hdu.edu.cn/showproblem.php?pid=3357

//3357
#include <cstdio>
#include <cstring>
using namespace std;

const int N=250;
int g[N][N];
int main()
{
    int n,m,C=0;
    while(scanf("%d%d",&n,&m),n||m)
    {
        memset(g,0,sizeof(g));
        for(int i=1;i<=n;i++) g[i][i]=1;
        int cnt=0;
        while(m--)
        {
            int u,v;
            scanf("%d%d",&u,&v);
            if(g[v][u])
            {
                cnt++;
                continue;
            }
            if(g[u][v]) continue;
            g[u][v]=1;
            for(int i=1;i<=n;i++) if(g[i][u])
                for(int j=1;j<=n;j++) if(g[v][j]) g[i][j]=1;
        }
        printf("%d. %d\n",++C,cnt);
    }
    return 0;
}