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

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
using namespace std;
using ll = long long;
using P = pair<ll, ll>;

// auto mod int
// https://youtu.be/L8grWxBlIZ4?t=9858
// https://youtu.be/ERZuLAxZffQ?t=4807 : optimize
// https://youtu.be/8uowVvQ_-Mo?t=1329 : division
const ll mod = 1000000007;
struct mint {
  ll x; // typedef long long ll;
  mint(ll 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 { return mint(*this) += a; }
  mint operator-(const mint a) const { return mint(*this) -= a; }
  mint operator*(const mint a) const { return mint(*this) *= a; }
  mint pow(ll t) const {
    if (!t)
      return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }

  // for prime mod
  mint inv() const { return pow(mod - 2); }
  mint &operator/=(const mint a) { return *this *= a.inv(); }
  mint operator/(const mint a) const { return mint(*this) /= a; }
};
istream &operator>>(istream &is, const mint &a) { return is >> a.x; }
ostream &operator<<(ostream &os, const mint &a) { return os << a.x; }
// combination mod prime
// https://www.youtube.com/watch?v=8uowVvQ_-Mo&feature=youtu.be&t=1619
struct combination {
  vector<mint> fact, ifact;
  combination(int n) : fact(n + 1), ifact(n + 1) {
    assert(n < mod);
    fact[0] = 1;
    for (int i = 1; i <= n; ++i)
      fact[i] = fact[i - 1] * i;
    ifact[n] = fact[n].inv();
    for (int i = n; i >= 1; --i)
      ifact[i - 1] = ifact[i] * i;
  }
  mint operator()(int n, int k) {
    if (k < 0 || k > n)
      return 0;
    return fact[n] * ifact[k] * ifact[n - k];
  }
};
// struct combination c(200005);

ll gcd(ll a, ll b) {
  if (a < b)
    return gcd(b, a);
  ll r = 1;
  while (r != 0) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
ll modpow(ll a, ll n) {
  ll res = 1;
  while (n > 0) {
    if (n & 1)
      res = res * a % mod;
    a = a * a % mod;
    n >>= 1;
  }
  return res;
}
ll absll(ll a) {
  if (a >= 0)
    return a;
  return -a;
}
ll sign(ll n) {
  if (n >= 0) {
    return 1;
  } else {
    return -1;
  }
}

P grad(ll x, ll y) {
  if (x < 0) {
    x = -x, y = -y;
  }
  if (x == 0 && y == 0) {
    // dumy
  } else if (x == 0) {
    y = -1;
  } else if (y == 0) {
    x = 1;
  } else {
    ll g = gcd(abs(x), abs(y));
    x /= g;
    y /= g;
  }
  // cout << x << "," << y << endl;
  return P(x, y);
}

P othgonal(P p) {
  ll x = -p.second, y = p.first;
  if (x == 0)
    y = 1;
  else if (x < 0) {
    x = -x;
    y = -y;
  }
  return P(x, y);
}

int main() {
  int n;
  cin >> n;

  std::map<P, P> dist;
  int zero = 0;
  rep(i, n) {
    ll a, b;
    cin >> a >> b;
    if (a == 0 && b == 0)
      zero++;
    else {
      P g = grad(a, b);
      if (g.second < 0) {
        dist[othgonal(g)].second++;
      } else {
        dist[g].first++;
      }
    }
  }

  mint ans = 1;
  for (auto itr : dist) {
    P val = itr.second;
    // cout << val.first << "," << val.second << "|" << itr.first.first << ","
    // << itr.first.second << endl;
    mint tmp = 1;
    tmp += modpow(2, val.first) - 1;
    tmp += modpow(2, val.second) - 1;
    ans *= tmp;
  }
  ans += zero - 1;
  cout << ans << endl;
  return 0;
}


Error: 0

Fixed submission:

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
using namespace std;
typedef long long ll;
// using P = pair<int,int>;

// auto mod int
// https://youtu.be/L8grWxBlIZ4?t=9858
// https://youtu.be/ERZuLAxZffQ?t=4807 : optimize
// https://youtu.be/8uowVvQ_-Mo?t=1329 : division
const int mod = 1000000007;
struct mint {
  ll x; // typedef long long ll;
  mint(ll 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 { return mint(*this) += a; }
  mint operator-(const mint a) const { return mint(*this) -= a; }
  mint operator*(const mint a) const { return mint(*this) *= a; }
  mint pow(ll t) const {
    if (!t)
      return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }

  // for prime mod
  mint inv() const { return pow(mod - 2); }
  mint &operator/=(const mint a) { return *this *= a.inv(); }
  mint operator/(const mint a) const { return mint(*this) /= a; }
};
istream &operator>>(istream &is, const mint &a) { return is >> a.x; }
ostream &operator<<(ostream &os, const mint &a) { return os << a.x; }
// combination mod prime
// https://www.youtube.com/watch?v=8uowVvQ_-Mo&feature=youtu.be&t=1619

long long gcd(long long u, long long v) {
  if (u <= 0 || v <= 0)
    return 0;
  if (u == 1 || v == 1)
    return 1;
  long long d = 1, t;
  while ((u % 2) == 0 &&
         (v % 2) == 0) { // u, v どちらかが奇数になるまで2で割る。
    d *= 2;
    u /= 2;
    v /= 2; // d に除数を記憶しておく
  }
  if ((u % 2) != 0)
    t = -v;
  else
    t = u;
  while (t != 0) {
    while ((abs(t) % 2) == 0)
      t /= 2;
    if (t > 0)
      u = t;
    else
      v = -t;
    t = u - v;
  }
  return u * d;
}

int main() {
  int n;
  cin >> n;
  long long a[n], b[n];
  rep(i, n) { cin >> a[i] >> b[i]; }

  std::map<pair<int, int>, int> dist;
  rep(i, n) {
    ll g = gcd(abs(a[i]), abs(b[i]));
    ll c = a[i] / g;
    ll d = b[i] / g;
    if (c < 0) {
      c = -c, d = -d;
    }
    dist[std::make_pair(c, d)]++;
    // cout << "gcd:" << g << endl;
  }

  mint ans = 1;
  for (auto itr = dist.begin(); itr != dist.end(); ++itr) {
    ll c = itr->first.first, d = itr->first.second;
    int val = itr->second;
    if (val == 0)
      continue;
    // cout << c << "," << d << "=" << val << endl;
    if (d < 0) {
      c = -c;
      d = -d;
    }
    auto p = make_pair(d, -c);
    if (c < 0) {
      if (dist[p] == 0) {
        ans *= (1 << val);
        // cout << "no-pair(-)" << endl;
      } else {
        // cout << "2nd" << endl;
      }
    } else {
      if (dist[p] == 0) {
        ans *= (1 << val);
        // cout << "no-pair(+)" << endl;
      } else {
        ans *= (1 << val) - 1 + (1 << dist[p]) - 1 + 1;
        // cout << "pair" << val << ","<< dist[p] << endl;
      }
    }
    // cout << "ans: " << ans << endl << endl;
  }
  cout << (ans - 1) << endl;
  return 0;
}