L2-038 病毒溯源

#include <bits/stdc++.h>
using namespace std;
vector<int> vec[10010],ans;//矩阵
int vis[10010];
int maxLen = 0;
void dfs(int root,vector<int> &v) {
	if(v.size() > maxLen){
		ans.clear();
		ans = v;
		maxLen = v.size();
	}
	for (int i = 0; i < vec[root].size(); i++) {
		v.push_back(vec[root][i]);
		dfs(vec[root][i], v);
		v.pop_back();
	}
}
int main() {
	int n;
	cin >> n;
	for (int i = 0; i < n; i++) {//i起始
		int t;
		cin >> t;
		for (int j = 0; j < t; j++) {
			int tno;
			cin >> tno;
			vec[i].push_back(tno);
			vis[tno] = 1;
		}
		//将里面的元素进行排序
		sort(vec[i].begin(),vec[i].end());
	}
	//找到根
	int root = 0;
	for (int i = 0; i < n; i++) {
		if (vis[i] == 0) {
			root = i;
			break;
		}
	}
	vector<int> v;
	v.push_back(root);
	dfs(root,v);
	cout << maxLen << '\n';
	for (int i = 0; i < ans.size(); i++) {
		cout << ans[i];
		if (i < ans.size()-1) cout << " ";
	}
	return 0;
}