Problem p02574 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
#define rep(i, n) for (long long int i = 0; i < n; i++)
#define _rep(i, m, n) for (long long int i = m; i < n; i++)
using namespace std;
typedef long long ll;
typedef pair<int, int> P;
const ll mod = 1000000007;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
string Yes[2] = {"Yes", "No"};

ll gcd(ll A, ll B) {
  if (B == 0)
    return A;
  return gcd(B, A % B);
}
ll lcm(ll A, ll B) { return A * B / gcd(A, B); }
template <typename T> T pow(T a, ll n, T e = 1) {
  T ret = e;
  while (n) {
    if (n & 1)
      ret *= a;
    a *= a;
    n >>= 1;
  }
  return ret;
}

template <int mod> struct ModInt {
  int x;
  ModInt() : x(0) {}
  ModInt(long long x_) {
    if ((x = x_ % mod + mod) >= mod)
      x -= mod;
  }
  ModInt &operator+=(ModInt rhs) {
    if ((x += rhs.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator-=(ModInt rhs) {
    if ((x -= rhs.x) < 0)
      x += mod;
    return *this;
  }
  ModInt &operator*=(ModInt rhs) {
    x = (unsigned long long)x * rhs.x % mod;
    return *this;
  }
  ModInt &operator/=(ModInt rhs) {
    x = (unsigned long long)x * rhs.inv().x % mod;
    return *this;
  }

  ModInt operator-() const { return -x < 0 ? mod - x : -x; }
  ModInt operator+(ModInt rhs) const { return ModInt(*this) += rhs; }
  ModInt operator-(ModInt rhs) const { return ModInt(*this) -= rhs; }
  ModInt operator*(ModInt rhs) const { return ModInt(*this) *= rhs; }
  ModInt operator/(ModInt rhs) const { return ModInt(*this) /= rhs; }
  bool operator==(ModInt rhs) const { return x == rhs.x; }
  bool operator!=(ModInt rhs) const { return x != rhs.x; }
  ModInt inv() const { return pow(*this, mod - 2); }

  friend ostream &operator<<(ostream &s, ModInt<mod> a) {
    s << a.x;
    return s;
  }
  friend istream &operator>>(istream &s, ModInt<mod> &a) {
    s >> a.x;
    return s;
  }
};

using mint = ModInt<1000000007>;
using Graph = vector<vector<int>>;
Graph G;

/*------------------------------------------------------------------*/
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int n;
  cin >> n;
  vector<int> a(n);
  int max_a = 0;
  rep(i, n) {
    cin >> a[i];
    max_a = max(max_a, a[i]);
  }
  vector<int> d(max_a + 1, 0);
  rep(i, max_a + 1) d[i] = i;

  for (int i = 2; i * i <= max_a; i++) {
    if (d[i] < i)
      continue;
    for (int j = i * i; j <= max_a; j += i) {
      if (d[j] == j)
        d[j] = i;
    }
  }
  vector<int> count(max_a + 1, 0);
  rep(i, n) {
    int x = a[i];
    while (x > 1) {
      count[d[x]]++;
      int cur = d[x];
      while (x % cur == 0) {
        x /= cur;
      }
    }
  }
  // rep(i, max_a + 1) cout << count[i] << endl;
  bool flag = true;
  rep(i, max_a + 1) {
    if (count[i] >= 2)
      flag = false;
  }
  int GCD = a[0];
  rep(i, n) GCD = gcd(a[i], GCD);

  if (flag)
    cout << "pairwise coprime" << endl;
  else if (GCD == 1)
    cout << "setwise coprime" << endl;
  else
    cout << "not coprime" << endl;
}

Error: 0

Fixed submission:

#include <bits/stdc++.h>
#define rep(i, n) for (long long int i = 0; i < n; i++)
#define _rep(i, m, n) for (long long int i = m; i < n; i++)
using namespace std;
typedef long long ll;
typedef pair<int, int> P;
const ll mod = 1000000007;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
string Yes[2] = {"Yes", "No"};

ll gcd(ll A, ll B) {
  if (B == 0)
    return A;
  return gcd(B, A % B);
}
ll lcm(ll A, ll B) { return A * B / gcd(A, B); }
template <typename T> T pow(T a, ll n, T e = 1) {
  T ret = e;
  while (n) {
    if (n & 1)
      ret *= a;
    a *= a;
    n >>= 1;
  }
  return ret;
}

template <int mod> struct ModInt {
  int x;
  ModInt() : x(0) {}
  ModInt(long long x_) {
    if ((x = x_ % mod + mod) >= mod)
      x -= mod;
  }
  ModInt &operator+=(ModInt rhs) {
    if ((x += rhs.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator-=(ModInt rhs) {
    if ((x -= rhs.x) < 0)
      x += mod;
    return *this;
  }
  ModInt &operator*=(ModInt rhs) {
    x = (unsigned long long)x * rhs.x % mod;
    return *this;
  }
  ModInt &operator/=(ModInt rhs) {
    x = (unsigned long long)x * rhs.inv().x % mod;
    return *this;
  }

  ModInt operator-() const { return -x < 0 ? mod - x : -x; }
  ModInt operator+(ModInt rhs) const { return ModInt(*this) += rhs; }
  ModInt operator-(ModInt rhs) const { return ModInt(*this) -= rhs; }
  ModInt operator*(ModInt rhs) const { return ModInt(*this) *= rhs; }
  ModInt operator/(ModInt rhs) const { return ModInt(*this) /= rhs; }
  bool operator==(ModInt rhs) const { return x == rhs.x; }
  bool operator!=(ModInt rhs) const { return x != rhs.x; }
  ModInt inv() const { return pow(*this, mod - 2); }

  friend ostream &operator<<(ostream &s, ModInt<mod> a) {
    s << a.x;
    return s;
  }
  friend istream &operator>>(istream &s, ModInt<mod> &a) {
    s >> a.x;
    return s;
  }
};

using mint = ModInt<1000000007>;
using Graph = vector<vector<int>>;
Graph G;

/*------------------------------------------------------------------*/
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int n;
  cin >> n;
  vector<int> a(n);
  int max_a = 0;
  rep(i, n) {
    cin >> a[i];
    max_a = max(max_a, a[i]);
  }
  vector<int> d(max_a + 1, 0);
  rep(i, max_a + 1) d[i] = i;

  for (int i = 2; i * i < max_a; i++) {
    if (d[i] < i)
      continue;
    for (int j = i * i; j < max_a; j += i) {
      if (d[j] == j)
        d[j] = i;
    }
  }
  vector<int> count(max_a + 1, 0);
  rep(i, n) {
    int x = a[i];
    while (x > 1) {
      count[d[x]]++;
      int cur = d[x];
      while (x % cur == 0) {
        x /= cur;
        // cout << x << " " << cur << endl;
      }
    }
  }
  // rep(i, max_a + 1) cout << count[i] << endl;
  vector<int> seen(max_a, false);
  bool flag = true;
  rep(i, n) {
    if (count[i] >= 2)
      flag = false;
  }
  int GCD = a[0];
  rep(i, n) GCD = gcd(a[i], GCD);

  if (flag)
    cout << "pairwise coprime" << endl;
  else if (GCD == 1)
    cout << "setwise coprime" << endl;
  else
    cout << "not coprime" << endl;
}