Problem p02972 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
// type alias
typedef long long LL;
typedef pair<int, int> II;
typedef tuple<int, int, int> III;
typedef vector<int> VI;
typedef vector<string> VS;
typedef unordered_map<int, int> MAPII;
typedef unordered_set<int> SETI;
template <class T> using VV = vector<vector<T>>;
// minmax
template <class T> inline T SMIN(T &a, const T b) {
  return a = (a > b) ? b : a;
}
template <class T> inline T SMAX(T &a, const T b) {
  return a = (a < b) ? b : a;
}
// repetition
#define FORE(i, a, b) for (int i = (a); i <= (b); ++i)
#define REPE(i, n) for (int i = 0; i <= (n); ++i)
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define FORR(x, arr) for (auto &x : arr)
#define SZ(a) int((a).size())
// collection
#define ALL(c) (c).begin(), (c).end()
// DP
#define MINUS(dp) memset(dp, -1, sizeof(dp))
#define ZERO(dp) memset(dp, 0, sizeof(dp))
// stdout
#define println(args...) fprintf(stdout, ##args), putchar('\n');
// debug cerr
template <class Iter> void __kumaerrc(Iter begin, Iter end) {
  for (; begin != end; ++begin) {
    cerr << *begin << ',';
  }
  cerr << endl;
}
void __kumaerr(istream_iterator<string> it) {
  (void)it;
  cerr << endl;
}
template <typename T, typename... Args>
void __kumaerr(istream_iterator<string> it, T a, Args... args) {
  cerr << *it << "=" << a << ", ", __kumaerr(++it, args...);
}
template <typename S, typename T>
std::ostream &operator<<(std::ostream &_os, const std::pair<S, T> &_p) {
  return _os << "{" << _p.first << ',' << _p.second << "}";
}
#define __KUMATRACE__ true
#ifdef __KUMATRACE__
#define dump(args...)                                                          \
  {                                                                            \
    string _s = #args;                                                         \
    replace(_s.begin(), _s.end(), ',', ' ');                                   \
    stringstream _ss(_s);                                                      \
    istream_iterator<string> _it(_ss);                                         \
    __kumaerr(_it, args);                                                      \
  }
#define dumpc(ar)                                                              \
  {                                                                            \
    cerr << #ar << ": ";                                                       \
    FORR(x, (ar)) { cerr << x << ','; }                                        \
    cerr << endl;                                                              \
  }
#define dumpC(beg, end)                                                        \
  {                                                                            \
    cerr << "~" << #end << ": ";                                               \
    __kumaerrc(beg, end);                                                      \
  }
#else
#define dump(args...)
#define dumpc(ar)
#define dumpC(beg, end)
#endif

// $ cp-batch PreparingBoxes | diff PreparingBoxes.out -
// $ g++ -std=c++14 -Wall -O2 -D_GLIBCXX_DEBUG -fsanitize=address
// PreparingBoxes.cpp && ./a.out

/*

 7/20/2019

 5:12-5:28 WA
 8:35 AC

 */

const int MAX_N = 1e6 + 1;
int A[MAX_N];
int N;

int X[MAX_N];
void solve() {
  ZERO(X);
  int sufn = (N + 1) / 2;
  int i = N;
  while (sufn--) {
    X[i] = A[i];
    --i;
  }
  while (i >= 1) {
    int sum = 0;
    for (int j = 2 * i; j <= N; j += i)
      sum += X[j];
    X[i] = sum ^ A[i];
    --i;
  }

  //  dumpC(X+1,X+N+1);
  FORE(i, 1, N) {
    int sum = 0;
    for (int j = i; j <= N; j += i)
      sum ^= X[j];
    //    dump(i,A[i],sum);
    assert(A[i] == sum);
  }

  VI res;
  FORE(i, 1, N) if (X[i]) res.push_back(i);
  println("%d", SZ(res));
  REP(i, SZ(res)) println("%d", res[i]);
}
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
int genRandNum(int lb, int ub) {
  assert(lb < ub);
  // Helper to generate random integer in range [lb, ub)
  int x = rnd() % (int)(ub - lb);
  return x + lb;
}
vector<int> genRandSeq(int size, int lb, int ub) {
  if (size == 0)
    return {};
  vector<int> res(size);
  generate(res.begin(), res.end(), [&]() { return genRandNum(lb, ub); });
  return res;
}
void test() {
  N = genRandNum(1, (int)2e5);
  VI AA = genRandSeq(N, 0, 2);
  REP(i, N) A[i + 1] = AA[i];
  dumpc(AA);
  solve();
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout << setprecision(12) << fixed;

  //  while(true) test();

  cin >> N;
  REP(i, N) cin >> A[i + 1];
  solve();

  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
// type alias
typedef long long LL;
typedef pair<int, int> II;
typedef tuple<int, int, int> III;
typedef vector<int> VI;
typedef vector<string> VS;
typedef unordered_map<int, int> MAPII;
typedef unordered_set<int> SETI;
template <class T> using VV = vector<vector<T>>;
// minmax
template <class T> inline T SMIN(T &a, const T b) {
  return a = (a > b) ? b : a;
}
template <class T> inline T SMAX(T &a, const T b) {
  return a = (a < b) ? b : a;
}
// repetition
#define FORE(i, a, b) for (int i = (a); i <= (b); ++i)
#define REPE(i, n) for (int i = 0; i <= (n); ++i)
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define FORR(x, arr) for (auto &x : arr)
#define SZ(a) int((a).size())
// collection
#define ALL(c) (c).begin(), (c).end()
// DP
#define MINUS(dp) memset(dp, -1, sizeof(dp))
#define ZERO(dp) memset(dp, 0, sizeof(dp))
// stdout
#define println(args...) fprintf(stdout, ##args), putchar('\n');
// debug cerr
template <class Iter> void __kumaerrc(Iter begin, Iter end) {
  for (; begin != end; ++begin) {
    cerr << *begin << ',';
  }
  cerr << endl;
}
void __kumaerr(istream_iterator<string> it) {
  (void)it;
  cerr << endl;
}
template <typename T, typename... Args>
void __kumaerr(istream_iterator<string> it, T a, Args... args) {
  cerr << *it << "=" << a << ", ", __kumaerr(++it, args...);
}
template <typename S, typename T>
std::ostream &operator<<(std::ostream &_os, const std::pair<S, T> &_p) {
  return _os << "{" << _p.first << ',' << _p.second << "}";
}
#define __KUMATRACE__ true
#ifdef __KUMATRACE__
#define dump(args...)                                                          \
  {                                                                            \
    string _s = #args;                                                         \
    replace(_s.begin(), _s.end(), ',', ' ');                                   \
    stringstream _ss(_s);                                                      \
    istream_iterator<string> _it(_ss);                                         \
    __kumaerr(_it, args);                                                      \
  }
#define dumpc(ar)                                                              \
  {                                                                            \
    cerr << #ar << ": ";                                                       \
    FORR(x, (ar)) { cerr << x << ','; }                                        \
    cerr << endl;                                                              \
  }
#define dumpC(beg, end)                                                        \
  {                                                                            \
    cerr << "~" << #end << ": ";                                               \
    __kumaerrc(beg, end);                                                      \
  }
#else
#define dump(args...)
#define dumpc(ar)
#define dumpC(beg, end)
#endif

// $ cp-batch PreparingBoxes | diff PreparingBoxes.out -
// $ g++ -std=c++14 -Wall -O2 -D_GLIBCXX_DEBUG -fsanitize=address
// PreparingBoxes.cpp && ./a.out

/*

 7/20/2019

 5:12-5:28 WA
 8:35 AC

 */

const int MAX_N = 1e6 + 1;
int A[MAX_N];
int N;

int X[MAX_N];
void solve() {
  ZERO(X);
  int sufn = (N + 1) / 2;
  int i = N;
  while (sufn--) {
    X[i] = A[i];
    --i;
  }
  while (i >= 1) {
    int sum = 0;
    for (int j = 2 * i; j <= N; j += i)
      sum ^= X[j];
    X[i] = sum ^ A[i];
    --i;
  }

  //  dumpC(X+1,X+N+1);
  FORE(i, 1, N) {
    int sum = 0;
    for (int j = i; j <= N; j += i)
      sum ^= X[j];
    //    dump(i,A[i],sum);
    assert(A[i] == sum);
  }

  VI res;
  FORE(i, 1, N) if (X[i]) res.push_back(i);
  println("%d", SZ(res));
  REP(i, SZ(res)) println("%d", res[i]);
}
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
int genRandNum(int lb, int ub) {
  assert(lb < ub);
  // Helper to generate random integer in range [lb, ub)
  int x = rnd() % (int)(ub - lb);
  return x + lb;
}
vector<int> genRandSeq(int size, int lb, int ub) {
  if (size == 0)
    return {};
  vector<int> res(size);
  generate(res.begin(), res.end(), [&]() { return genRandNum(lb, ub); });
  return res;
}
void test() {
  N = genRandNum(1, (int)2e5);
  VI AA = genRandSeq(N, 0, 2);
  REP(i, N) A[i + 1] = AA[i];
  dumpc(AA);
  solve();
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout << setprecision(12) << fixed;

  //  while(true) test();

  cin >> N;
  REP(i, N) cin >> A[i + 1];
  solve();

  return 0;
}