代码如下 （本蒟蒻刚学拓扑排序）

#include<bits/stdc++.h>
using namespace std;

int deg[10000],maxx = 0x3f3f3f3f,sorted = 0;
vector<int> v[10000];
bool vis[10000];

void topsort()
{
    queue<int> q;
    while(1)
    {
        //cout<<"topsorting....."<<endl;
        for(int i = 1; i <= maxx; i++)
        {
           // cout<<"chosing....."<<endl;
            if(deg[i] == 0 && !vis[i])
            {
                q.push(i);
                vis[i] = 1;
                sorted++;
            }
        }
        if(q.empty())
        {
            //cout<<"unchosed....."<<endl;
            break;
        }
        while(!q.empty())
        {
            //cout<<"deleting....."<<endl;
            int st = q.front();
            q.pop();
            for(int i = 0; i <= v[st].size()-1; i++)
            {
                int u = v[st][i];
                deg[u]--;
            }
        }
    }

    return ;
}
int main(){
    int n;
    cin>>n;
    for(int i = 0; i <= n-1; i++)
    {
        int x,m;
        cin>>x>>m;
        maxx = min(x,maxx);
        for(int i = 0; i <= m-1; i++)
        {
            int a;
            cin>>a;
            deg[a]++;
            v[x].push_back(a);
        }
    }
    topsort();
    if(sorted == n)
    {
        cout<<"YES"<<endl;
        return 0;
    }
    cout<<n-sorted<<endl;

    return 0;
}