70pts求调

#include <iostream>
#include <vector>
#include <queue>
using namespace std;
const int N = 505;
int n, m;
int in[N];
vector<int> G[N];
queue<int> q;
int main()
{
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        int u;
        cin >> u >> m;
        for (int j = 1; j <= m; j++)
        {
            int v;
            cin >> v;
            G[u].push_back(v);
            in[v]++;
        }
    }
    for (int i = 0; i <= n; i++)
    {
        if (!in[i])
        {
            q.push(i);
        }
    }
    while (!q.empty())
    {
        int u = q.front();
        q.pop();
        for (int i = 0; i < G[u].size(); i++)
        {
            int v = G[u][i];
            in[v]--;
            if (!in[v])
            {
                q.push(v);
            }
        }
    }
    int sum = 0;
    for (int i = 0; i <= n; i++)
    {
        if (in[i])
        {
            sum++;
        }
    }
    if (!sum)
    {
        cout << "YES";
    }
    else
    {
        cout << sum;
    }
    return 0;
}