Implementation
P_2_Ebola_Outbreak.cpp
C++
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int INF = 0x3f3f3f3f; //❄️
vector<int> parent;
int find(int x) {
if(parent[x] == x) return x;
return parent[x] = find(parent[x]);
}
void unite(int x, int y) {
x = find(x); y = find(y);
parent[x] = y;
}
int main() {
ios::sync_with_stdio(0); cin.tie(0);
int n, m; cin >> n >> m;
parent.resize(n + 1);
for (int i = 0; i <= n; i++) parent[i] = i;
for (int i = 0; i < m; i++) {
int c; cin >> c;
int leader; cin >> leader;
for (int j = 1; j < c; j++) {
int k; cin >> k;
unite(leader, k);
}
}
vector<int> ans;
int root = find(1);
for (int i = 1; i <= n; i++) {
if (find(i) == root) ans.push_back(i);
}
sort(ans.begin(), ans.end());
cout << ans.size() << '\n';
for (int i = 0; i < ans.size(); i++) cout << ans[i] << " \n"[i == ans.size() - 1];
return 0;
}