BOJ 1418 - K-세준수 [C++]

문제

링크

풀이

#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;
 
void solve(void) {
  int n; cin >> n;
  int k; cin >> k;
 
  vector<int> v(n+1, 0);
  for (int i=2; i<=n; i++) {
    if (v[i]) continue;
    for (int j=i; j<=n; j+=i) v[j] = max(v[j], i);
  }
 
  int ans = 0;
  for (int i=1; i<=n; i++) {
    if (v[i] <= k) ans++;
  }
  cout << ans;
}
 
int main(void) {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
 
  solve();
  return 0;
}