Problem p02679 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
using namespace std;
#define rep(i, N) for (int i = 0; i < int(N); ++i)
#define rep1(i, N) for (int i = 1; i < int(N); ++i)
#define all(a) (a).begin(), (a).end()
#define print(v)                                                               \\
  {                                                                            \\
    cerr << #v << ": [ ";                                                      \\
    for (auto _ : v)                                                           \\
      cerr << _ << ", ";                                                       \\
    cerr << "]" << endl;                                                       \\
  }
#define printpair(v)                                                           \\
  {                                                                            \\
    cerr << #v << ": [ ";                                                      \\
    for (auto _ : v)                                                           \\
      cerr << "{" << _.first << "," << _.second << "}"                         \\
           << ", ";                                                            \\
    cerr << "]" << endl;                                                       \\
  }
#define dump(x) cerr << #x << ": " << x << endl;
#define bit(k) (1LL << (k))
typedef long long ll;
typedef pair<int, int> i_i;
typedef pair<ll, ll> l_l;
template <class T> using vec = vector<T>;
template <class T> using vvec = vector<vec<T>>;
template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << "{" << p.first << ", " << p.second << "}";
  return os;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

const int INF = (ll)1e9;
const ll INFLL = (ll)1e18 + 1;
const ll MOD = (ll)1e9 + 7;
const double PI = acos(-1.0);
/*
const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
const string dir = "DRUL";
*/
struct mint {
  long long x;
  mint(long long _x = 0) : x((_x % MOD + MOD) % MOD) {}
  mint operator-() const { return mint(-x); }
  mint &operator+=(const mint a) {
    if ((x += a.x) >= MOD)
      x -= MOD;
    return *this;
  }
  mint &operator-=(const mint a) {
    if ((x += MOD - a.x) >= MOD)
      x -= MOD;
    return *this;
  }
  mint &operator*=(const mint a) {
    (x *= a.x) %= MOD;
    return *this;
  }
  mint operator+(const mint a) const {
    mint res(*this);
    return res += a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res -= a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res *= a;
  }
  mint modpow(long long t) const {
    if (!t)
      return 1;
    mint a = modpow(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }
  // for prime MOD
  mint inv() const { return modpow(MOD - 2); }
  mint &operator/=(const mint a) { return (*this) *= a.inv(); }
  mint operator/(const mint a) const {
    mint res(*this);
    return res /= a;
  }
  friend std::ostream &operator<<(std::ostream &os, const mint &a) {
    os << a.x;
    return os;
  }
};
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(20);
  ll N;
  cin >> N;
  vector<ll> A(N), B(N);
  map<pair<ll, l_l>, ll> mp;
  rep(i, N) {
    cin >> A[i] >> B[i];
    if (A[i] == 0 && B[i] == 0) {
      mp[{0, {0LL, 0LL}}]++;
      continue;
    }
    if (A[i] == 0 && B[i] != 0) {
      mp[{2, {0, 1}}]++;
      continue;
    }
    if (A[i] != 0 && B[i] == 0) {
      mp[{-2, {1, 0}}]++;
      continue;
    }
    ll G = gcd(abs(A[i]), abs(B[i]));
    A[i] /= G;
    B[i] /= G;
    if ((A[i] < 0 && B[i] > 0) || (A[i] > 0 && B[i] < 0)) {
      mp[{-1, {abs(A[i]), abs(B[i])}}]++;
    }
    if ((A[i] > 0 && B[i] > 0) || (A[i] < 0 && B[i] < 0)) {
      mp[{1, {abs(A[i]), abs(B[i])}}]++;
    }
  }
  mint ans = 1;
  // print(mp);
  mint ori = 0;
  for (auto &p : mp) {
    int fugo = p.first.first;
    ll a = p.first.second.first;
    ll b = p.first.second.second;
    ll cnt = p.second;
    if (cnt == -1)
      continue;
    if (cnt == 0)
      continue;
    // dump(p);
    if (fugo == 0) {
      ori = cnt;
      continue;
    }
    pair<ll, l_l> gyaku = {-fugo, {b, a}};
    // 逆符号で、逆にやつ{-fugo, {b,a}}が存在するかどうか
    if (mp[gyaku] > 0) {
      // dump(gyaku);
      ll cnt2 = mp[gyaku];
      ans *= mint(2).modpow(cnt) + mint(2).modpow(cnt2) - 1;
      mp[gyaku] = -1;
    } else {
      ans *= mint(2).modpow(cnt);
    }
  }
  ans += ori;
  ans = ans - 1;
  cout << ans << endl;
}

Error: 0

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
#define rep(i, N) for (int i = 0; i < int(N); ++i)
#define rep1(i, N) for (int i = 1; i < int(N); ++i)
#define all(a) (a).begin(), (a).end()
#define print(v)                                                               \\
  {                                                                            \\
    cerr << #v << ": [ ";                                                      \\
    for (auto _ : v)                                                           \\
      cerr << _ << ", ";                                                       \\
    cerr << "]" << endl;                                                       \\
  }
#define printpair(v)                                                           \\
  {                                                                            \\
    cerr << #v << ": [ ";                                                      \\
    for (auto _ : v)                                                           \\
      cerr << "{" << _.first << "," << _.second << "}"                         \\
           << ", ";                                                            \\
    cerr << "]" << endl;                                                       \\
  }
#define dump(x) cerr << #x << ": " << x << endl;
#define bit(k) (1LL << (k))
typedef long long ll;
typedef pair<int, int> i_i;
typedef pair<ll, ll> l_l;
template <class T> using vec = vector<T>;
template <class T> using vvec = vector<vec<T>>;
template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << "{" << p.first << ", " << p.second << "}";
  return os;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

const int INF = (ll)1e9;
const ll INFLL = (ll)1e18 + 1;
const ll MOD = (ll)1e9 + 7;
const double PI = acos(-1.0);
/*
const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
const string dir = "DRUL";
*/
struct mint {
  long long x;
  mint(long long _x = 0) : x((_x % MOD + MOD) % MOD) {}
  mint operator-() const { return mint(-x); }
  mint &operator+=(const mint a) {
    if ((x += a.x) >= MOD)
      x -= MOD;
    return *this;
  }
  mint &operator-=(const mint a) {
    if ((x += MOD - a.x) >= MOD)
      x -= MOD;
    return *this;
  }
  mint &operator*=(const mint a) {
    (x *= a.x) %= MOD;
    return *this;
  }
  mint operator+(const mint a) const {
    mint res(*this);
    return res += a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res -= a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res *= a;
  }
  mint modpow(long long t) const {
    if (!t)
      return 1;
    mint a = modpow(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }
  // for prime MOD
  mint inv() const { return modpow(MOD - 2); }
  mint &operator/=(const mint a) { return (*this) *= a.inv(); }
  mint operator/(const mint a) const {
    mint res(*this);
    return res /= a;
  }
  friend std::ostream &operator<<(std::ostream &os, const mint &a) {
    os << a.x;
    return os;
  }
};
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(20);

  int N;
  cin >> N;
  vector<ll> A(N), B(N);
  map<pair<int, l_l>, int> mp;
  rep(i, N) {
    cin >> A[i] >> B[i];
    ll G = gcd(abs(A[i]), abs(B[i]));
    A[i] /= G;
    B[i] /= G;
    if ((A[i] < 0 && B[i] > 0) || (A[i] > 0 && B[i] < 0)) {
      mp[{-1, {abs(A[i]), abs(B[i])}}]++;
    } else if (A[i] == 0 || B[i] == 0) {
      mp[{0, {0, 0}}]++;
    } else {
      mp[{1, {abs(A[i]), abs(B[i])}}]++;
    }
  }
  mint ans = 1;
  // print(mp);
  for (auto &p : mp) {
    int fugo = p.first.first;
    ll a = p.first.second.first;
    ll b = p.first.second.second;
    ll cnt = p.second;
    if (cnt == -1)
      continue;
    if (cnt == 0)
      continue;
    if (fugo == 0) {
      ans *= mint(2).modpow(cnt);
      continue;
    }
    // dump(p);
    pair<int, l_l> gyaku = {-fugo, {b, a}};
    // 逆符号で、逆にやつ{-fugo, {b,a}}が存在するかどうか
    if (mp[gyaku] > 0) {
      // dump(gyaku);
      ll cnt2 = mp[gyaku];
      ans *= mint(2).modpow(cnt) + mint(2).modpow(cnt2) - 1;
      mp[gyaku] = -1;
    } else {
      ans *= mint(2).modpow(cnt);
    }
    // dump(ans);
  }
  ans = ans - 1;

  cout << ans << endl;
}