BOJ 27494 - 2023년은 검은 토끼의 해 [C++]

문제

링크

풀이

#include <iostream>
#include <string>
using namespace std;
 
bool check(string s) {
  if (s.find_first_of('2') == string::npos) return false;
  s = s.substr(s.find_first_of('2'));
  if (s.find_first_of('0') == string::npos) return false;
  s = s.substr(s.find_first_of('0'));
  if (s.find_first_of('2') == string::npos) return false;
  s = s.substr(s.find_first_of('2'));
  if (s.find_first_of('3') == string::npos) return false;
  s = s.substr(s.find_first_of('3'));
 
  return true;
}
 
void solve(void) {
  int n; cin >> n;
 
  int ans = 0;
  for (int i=1; i<=n; i++) {
    if (check(to_string(i))) ans++;
  }
  cout << ans;
}
 
int main(void) {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
 
  solve();
  return 0;
}