BOJ 17511 - Capital [C++]

문제

링크

풀이

#include <iostream>
#include <set>
using namespace std;
 
void solve(void) {
  int n, m; cin >> n >> m;
  
  set<int> ans;
  for (int i=1; i<=n; i++) ans.insert(i);
  while (m--) {
    int a, b; cin >> a >> b;
    if (ans.count(b)) ans.erase(b);
  }
 
  cout << ans.size() << "\n";
  for (int x : ans) cout << x << " ";
}
 
int main(void) {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
 
  solve();
  return 0;
}