WA 了 21 个点。

#include<bits/stdc++.h>
#define endl '\n'
typedef long long ll;
using namespace std;
int n,x,v,cnt,ans[200005];
vector<int> g[200005];
bool vis[200005];
queue<int> q;
int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin >> n;
	for(int i = 1;i <= n;i++){
		cin >> x;
		for(int j = 1;j <= x;j++)cin >> v,g[i].push_back(v);
	}
	q.push(1);
	while(!q.empty()){
		int u = q.front();q.pop();
		if(u != 1)ans[++cnt] = u;
		for(int i = 0;i < g[u].size();i++){
			int v = g[u][i];
			if(!vis[v])vis[v] = true,q.push(v);
		}
	}
	for(int i = cnt;i >= 1;i--)cout << ans[i] << " ";
}