Problem p02642 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <algorithm>
#include <bits/stdc++.h>
#include <cmath>
#include <iostream>
#include <string>
#include <unordered_map>
#include <unordered_set>
using namespace std;
#define ll long long
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define FOR(i, a, b) for (ll i = (a); i < (b); i++)
#define FORR(i, a, b) for (ll i = (a); i <= (b); i++)
#define repR(i, n) for (ll i = n; i >= 0; i--)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define F first
#define S second
#define pb push_back
#define pu push
#define COUT(x) cout << (x) << "\n"
#define PQ priority_queue<ll>
#define PQR priority_queue<ll, vector<ll>, greater<ll>>
#define YES(n) cout << ((n) ? "YES\n" : "NO\n")
#define Yes(n) cout << ((n) ? "Yes\n" : "No\n")
#define mp make_pair
#define sz(x) (ll)(x).size()
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const ll MOD = 1000000007LL;
const ll INF = 1LL << 60;
using vll = vector<ll>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vvll = vector<vll>;
using vstr = vector<string>;
using vc = vector<char>;
using vvc = vector<vc>;
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
ll dx[4] = {0, 1, 0, -1};
ll dy[4] = {1, 0, -1, 0};
int main() {
  ll n;
  cin >> n;
  vll a(n);
  rep(i, n) cin >> a[i];
  sort(all(a));
  ll ans = 0;
  vll b(1000001);
  rep(i, n) {
    if (b[a[i]] == 0) {
      ans++;
      if (i + 1 < n) {
        if (a[i] == a[i + 1])
          ans--;
      }
    }
    ll now = 1;
    while (now * a[i] < 1000001) {
      b[now * a[i]] = 1;
      now++;
    }
  }
  COUT(ans);
}


Fixed submission:
#include <algorithm>
#include <bits/stdc++.h>
#include <cmath>
#include <iostream>
#include <string>
#include <unordered_map>
#include <unordered_set>
using namespace std;
#define ll long long
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define FOR(i, a, b) for (ll i = (a); i < (b); i++)
#define FORR(i, a, b) for (ll i = (a); i <= (b); i++)
#define repR(i, n) for (ll i = n; i >= 0; i--)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define F first
#define S second
#define pb push_back
#define pu push
#define COUT(x) cout << (x) << "\n"
#define PQ priority_queue<ll>
#define PQR priority_queue<ll, vector<ll>, greater<ll>>
#define YES(n) cout << ((n) ? "YES\n" : "NO\n")
#define Yes(n) cout << ((n) ? "Yes\n" : "No\n")
#define mp make_pair
#define sz(x) (ll)(x).size()
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const ll MOD = 1000000007LL;
const ll INF = 1LL << 60;
using vll = vector<ll>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vvll = vector<vll>;
using vstr = vector<string>;
using vc = vector<char>;
using vvc = vector<vc>;
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
ll dx[4] = {0, 1, 0, -1};
ll dy[4] = {1, 0, -1, 0};
int main() {
  ll n;
  cin >> n;
  vll a(n);
  rep(i, n) cin >> a[i];
  sort(all(a));
  ll ans = 0;
  vll b(1000001);
  rep(i, n) {
    if (i) {
      if (a[i] == a[i - 1])
        continue;
    }
    if (b[a[i]] == 0) {
      ans++;
      if (i + 1 < n) {
        if (a[i] == a[i + 1])
          ans--;
      }
    }
    ll now = 1;
    while (now * a[i] < 1000001) {
      b[now * a[i]] = 1;
      now++;
    }
  }
  COUT(ans);
}