poj 3660

水题，floyd

#include<cstring>#include<cstdio>#include<cmath>#include<algorithm>using namespace std;int g[110][110];int main(){    int i,j,k,n,m;    scanf("%d %d",&n,&m);    memset(g,-1,sizeof(g));    for(i=1;i<=m;i++){        int x,y;        scanf("%d %d",&x,&y);        g[x][y]=1;    }    for(k=1;k<=n;k++)        for(i=1;i<=n;i++)            for(j=1;j<=n;j++)                if(g[i][k]==1 && g[k][j]==1)                    g[i][j]=1;    int ans=0;    for(i=1;i<=n;i++){        int tmp=0;        for(j=1;j<=n;j++)            if(g[i][j]==1 || g[j][i]==1)                tmp++;        if(tmp==n-1)ans++;    }    printf("%d\n",ans);}