Problem p02467 (C++)

Buggy submission (status: Memory Limit Exceeded):
#include <bits/stdc++.h>

using namespace std;

class Prime {
private:
  vector<long long> divisor;

public:
  Prime(long long n) {
    for (long long i = 0; i < n; ++i)
      divisor.emplace_back(i);
    for (long long i = 2; i <= n / i; ++i)
      if (divisor[i] == i) {
        for (long long j = i * i; j < n; j += i)
          divisor[j] = i;
      }
  }

  bool is_prime(long long n) {
    if (n <= 1)
      return false;
    if (n < (long long)divisor.size())
      return divisor[n] == n;
    for (long long i = 2; i <= n / i; ++i)
      if (n % i == 0)
        return false;
    return true;
  }

  vector<long long> factor(long long n) {
    vector<long long> res;
    for (long long i = 2; i <= n / i && n >= (long long)divisor.size(); ++i) {
      while (n % i == 0) {
        res.emplace_back(i);
        n /= i;
      }
    }
    if (n >= (long long)divisor.size()) {
      res.emplace_back(n);
    } else {
      while (n > 1) {
        res.emplace_back(divisor[n]);
        n /= divisor[n];
      }
    }
    sort(res.begin(), res.end());
    return res;
  }

  vector<long long> get_divisors(long long n) {
    vector<long long> res;
    for (long long i = 2; i <= n / i && n >= (long long)divisor.size(); ++i) {
      if (n % i)
        continue;
      res.emplace_back(i);
      while (n % i == 0)
        n /= i;
    }
    if (n >= (long long)divisor.size()) {
      res.emplace_back(n);
    } else {
      while (n > 1) {
        long long d = divisor[n];
        res.emplace_back(d);
        while (n % d == 0)
          n /= d;
      }
    }
    sort(res.begin(), res.end());
    return res;
  }
};

int main() {
  int n;
  cin >> n;
  Prime prime(10000000);
  cout << n << ":";
  for (int f : prime.factor(n))
    cout << " " << f;
  cout << endl;
}

Fixed submission:
#include <bits/stdc++.h>

using namespace std;

class Prime {
private:
  vector<long long> divisor;

public:
  Prime(long long n) {
    for (long long i = 0; i < n; ++i)
      divisor.emplace_back(i);
    for (long long i = 2; i <= n / i; ++i)
      if (divisor[i] == i) {
        for (long long j = i * i; j < n; j += i)
          divisor[j] = i;
      }
  }

  bool is_prime(long long n) {
    if (n <= 1)
      return false;
    if (n < (long long)divisor.size())
      return divisor[n] == n;
    for (long long i = 2; i <= n / i; ++i)
      if (n % i == 0)
        return false;
    return true;
  }

  vector<long long> factor(long long n) {
    vector<long long> res;
    for (long long i = 2; i <= n / i && n >= (long long)divisor.size(); ++i) {
      while (n % i == 0) {
        res.emplace_back(i);
        n /= i;
      }
    }
    if (n >= (long long)divisor.size()) {
      res.emplace_back(n);
    } else {
      while (n > 1) {
        res.emplace_back(divisor[n]);
        n /= divisor[n];
      }
    }
    sort(res.begin(), res.end());
    return res;
  }

  vector<long long> get_divisors(long long n) {
    vector<long long> res;
    for (long long i = 2; i <= n / i && n >= (long long)divisor.size(); ++i) {
      if (n % i)
        continue;
      res.emplace_back(i);
      while (n % i == 0)
        n /= i;
    }
    if (n >= (long long)divisor.size()) {
      res.emplace_back(n);
    } else {
      while (n > 1) {
        long long d = divisor[n];
        res.emplace_back(d);
        while (n % d == 0)
          n /= d;
      }
    }
    sort(res.begin(), res.end());
    return res;
  }
};

int main() {
  int n;
  cin >> n;
  Prime prime(1000000);
  cout << n << ":";
  for (int f : prime.factor(n))
    cout << " " << f;
  cout << endl;
}