Problem p02972 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using Pi = pair<int, int>;
using Pl = pair<ll, ll>;
using vint = vector<int>;
using vvint = vector<vint>;
using vvvint = vector<vvint>;
using vdouble = vector<double>;
using vvdouble = vector<vdouble>;
using vvvdouble = vector<vvdouble>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using uint = unsigned int;
using ull = unsigned long long;

template <typename T> using uset = unordered_set<T>;
template <typename T1, typename T2> using umap = unordered_map<T1, T2>;

constexpr int INF = (1 << 30) - 1;
constexpr ll LLINF = 1LL << 60;
constexpr int dy[] = {1, 0, -1, 0, 1, -1, -1, 1};
constexpr int dx[] = {0, 1, 0, -1, 1, 1, -1, -1};
constexpr char el = '\n';
constexpr int mod = 1000000007;
constexpr int mod2 = 998244353;
template <typename T> T gcd(T a, T b) { return (b ? gcd(b, a % b) : a); }
template <typename T> T lcm(T a, T b) { return (a / gcd(a, b) * b); }
template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) {
  return (a > b && (a = b, true));
}
template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) {
  return (a < b && (a = b, true));
}

template <typename T> vector<T> makeVector(size_t a, T b) {
  return (vector<T>(a, b));
}
template <typename... Ts> auto makeVector(size_t a, Ts... ts) {
  return (vector<decltype(makeVector(ts...))>(a, makeVector(ts...)));
}

template <typename T> bool isin(T y, T x, T h, T w) {
  return (0 <= y && 0 <= x && y < h && x < w);
}
template <typename T> bool isin1(T y, T x, T h, T w) {
  return (0 < y && 0 < x && y <= h && x <= w);
}

template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  os << v[0];
  for (int i = 1; i < v.size(); i++)
    os << " " << v[i];
  return (os);
}

template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &u : v)
    is >> u;
  return (is);
}

template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  return (is >> p.first >> p.second);
}

void Main() {
  int N;
  cin >> N;
  vint A(N + 1);
  for (int i = 1; i <= N; i++)
    cin >> A[i];
  vector<bool> used(N + 1, false);

  for (int i = N; i > 0; i--) {
    int cnt = 0;
    for (int j = i + i; j <= N; j += i) {
      if (used[j])
        cnt++;
    }
    if ((cnt + A[i]) % 2 == 1) {
      used[i] = true;
    }
  }
  vint ans;
  for (int i = 1; i <= N; i++) {
    if (used[i])
      ans.push_back(i);
  }
  cout << ans.size() << endl;
  cout << ans << endl;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cout << fixed << setprecision(20);
  Main();
  return (0);
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using Pi = pair<int, int>;
using Pl = pair<ll, ll>;
using vint = vector<int>;
using vvint = vector<vint>;
using vvvint = vector<vvint>;
using vdouble = vector<double>;
using vvdouble = vector<vdouble>;
using vvvdouble = vector<vvdouble>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using uint = unsigned int;
using ull = unsigned long long;

template <typename T> using uset = unordered_set<T>;
template <typename T1, typename T2> using umap = unordered_map<T1, T2>;

constexpr int INF = (1 << 30) - 1;
constexpr ll LLINF = 1LL << 60;
constexpr int dy[] = {1, 0, -1, 0, 1, -1, -1, 1};
constexpr int dx[] = {0, 1, 0, -1, 1, 1, -1, -1};
constexpr char el = '\n';
constexpr int mod = 1000000007;
constexpr int mod2 = 998244353;
template <typename T> T gcd(T a, T b) { return (b ? gcd(b, a % b) : a); }
template <typename T> T lcm(T a, T b) { return (a / gcd(a, b) * b); }
template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) {
  return (a > b && (a = b, true));
}
template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) {
  return (a < b && (a = b, true));
}

template <typename T> vector<T> makeVector(size_t a, T b) {
  return (vector<T>(a, b));
}
template <typename... Ts> auto makeVector(size_t a, Ts... ts) {
  return (vector<decltype(makeVector(ts...))>(a, makeVector(ts...)));
}

template <typename T> bool isin(T y, T x, T h, T w) {
  return (0 <= y && 0 <= x && y < h && x < w);
}
template <typename T> bool isin1(T y, T x, T h, T w) {
  return (0 < y && 0 < x && y <= h && x <= w);
}

template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  if (v.size() == 0)
    return (os);
  os << v[0];
  for (int i = 1; i < v.size(); i++)
    os << " " << v[i];
  return (os);
}

template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &u : v)
    is >> u;
  return (is);
}

template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  return (is >> p.first >> p.second);
}

void Main() {
  int N;
  cin >> N;
  vint A(N + 1);
  for (int i = 1; i <= N; i++)
    cin >> A[i];
  vector<bool> used(N + 1, false);

  for (int i = N; i > 0; i--) {
    int cnt = 0;
    for (int j = i + i; j <= N; j += i) {
      if (used[j])
        cnt++;
    }
    if ((cnt + A[i]) % 2 == 1) {
      used[i] = true;
    }
  }
  vint ans;
  for (int i = 1; i <= N; i++) {
    if (used[i])
      ans.push_back(i);
  }
  cout << ans.size() << endl;
  cout << ans << endl;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cout << fixed << setprecision(20);
  Main();
  return (0);
}