[USACO08JAN]Cow Contest S Floyd

Cow Contest S
了解了Floyd的第二个用处，判断两点是否连通

#include 
using namespace std;
const int MAX=105,INF=0x3F3F3F3F;
bool g[MAX][MAX];
int n,e,ans;

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][j]||(g[i][k]&&g[k][j]);
}

int main() {
	cin>>n>>e;
	ans=n;
	for (int i=1;i<=e;i++) {
		int x,y;
		cin>>x>>y;
		g[x][y]=true;
	}
	for (int i=1;i<=n;i++)
		g[i][i]=true;
	floyd();
		
	for (int i=1;i<=n;i++)
		for (int j=1;j<=n;j++)
			if (!g[i][j]&&!g[j][i]) {
				ans--;
				break;
			}
	cout<