Problem p02574 (C++)

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

using namespace std;
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;

#define INF LONG_MAX
#define MOD 1000000007
#define rng(a) a.begin(), a.end()
#define rrng(a) a.end(), a.begin()
#define endl "\n"

int_fast64_t gcd(int_fast64_t a, int_fast64_t b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);

  int N;
  cin >> N;
  vector<int> A(N);
  for (int i = 0; i < N; i++)
    cin >> A[i];
  sort(rng(A));

  vector<int> a(1000001);
  vector<bool> isprime(1000001, true);
  isprime[0] = isprime[1] = false;
  for (int i = 0; i <= 1000000; i++) {
    if (isprime[i])
      for (int j = i + i; j <= 1000000; j += i) {
        isprime[j] = false;
        a[j] = i;
      }
  }

  vector<vector<pii>> div(1000001);
  for (int i = 0; i <= 1000000; i++) {
    int n = i;
    map<int, int> ans;
    while (a[n] != 0) {
      ans[a[n]]++;
      n = n / a[n];
    }
    if (n != 0 && n != 1)
      ans[n]++;
    for (auto it : ans)
      div[i].push_back({it.first, it.second});
  }

  vector<int> prime;
  for (int i = 0; i <= 1000000; i++)
    if (isprime[i])
      prime.push_back(i);

  bool pairwise = true;
  vector<int> x(100001, 0);

  for (auto it : div[A[0]])
    x[it.first] = max(x[it.first], it.second);

  for (int i = 0; i < N - 1; i++) {
    for (auto it : div[A[i + 1]])
      if (min(x[it.first], it.second) != 0)
        pairwise = false;
    for (auto it : div[A[i + 1]])
      x[it.first] = max(x[it.first], it.second);
  }

  int GCD = A[0];
  for (int i = 0; i < N - 1; i++)
    GCD = gcd(GCD, A[i + 1]);
  bool setwise = (GCD == 1);

  if (pairwise)
    cout << "pairwise coprime" << endl;
  else if (setwise)
    cout << "setwise coprime" << endl;
  else
    cout << "not coprime" << endl;

  return 0;
}


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

using namespace std;
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;

#define INF LONG_MAX
#define MOD 1000000007
#define rng(a) a.begin(), a.end()
#define rrng(a) a.end(), a.begin()
#define endl "\n"

int_fast64_t gcd(int_fast64_t a, int_fast64_t b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);

  int N;
  cin >> N;
  vector<int> A(N);
  for (int i = 0; i < N; i++)
    cin >> A[i];
  sort(rng(A));

  vector<int> a(1000001);
  vector<bool> isprime(1000001, true);
  isprime[0] = isprime[1] = false;
  for (int i = 0; i <= 1000000; i++) {
    if (isprime[i])
      for (int j = i + i; j <= 1000000; j += i) {
        isprime[j] = false;
        a[j] = i;
      }
  }

  vector<vector<pii>> div(1000001);
  for (int i = 0; i <= 1000000; i++) {
    int n = i;
    map<int, int> ans;
    while (a[n] != 0) {
      ans[a[n]]++;
      n = n / a[n];
    }
    if (n != 0 && n != 1)
      ans[n]++;
    for (auto it : ans)
      div[i].push_back({it.first, it.second});
  }

  vector<int> prime;
  for (int i = 0; i <= 1000000; i++)
    if (isprime[i])
      prime.push_back(i);

  bool pairwise = true;
  vector<int> x(1000001, 0);

  for (auto it : div[A[0]])
    x[it.first] = max(x[it.first], it.second);

  for (int i = 0; i < N - 1; i++) {
    for (auto it : div[A[i + 1]])
      if (min(x[it.first], it.second) != 0)
        pairwise = false;
    for (auto it : div[A[i + 1]])
      x[it.first] = max(x[it.first], it.second);
  }

  int GCD = A[0];
  for (int i = 0; i < N - 1; i++)
    GCD = gcd(GCD, A[i + 1]);
  bool setwise = (GCD == 1);

  if (pairwise)
    cout << "pairwise coprime" << endl;
  else if (setwise)
    cout << "setwise coprime" << endl;
  else
    cout << "not coprime" << endl;

  return 0;
}