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

#include <bits/stdc++.h>

int ri() {
  int n;
  scanf("%d", &n);
  return n;
}
#define MOD 1000000007

template <int mod> struct ModInt {
  int x;
  ModInt() : x(0) {}
  ModInt(long long y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
  ModInt &operator+=(const ModInt &p) {
    if ((x += p.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator-=(const ModInt &p) {
    if ((x += mod - p.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator*=(const ModInt &p) {
    x = (int)(1LL * x * p.x % mod);
    return *this;
  }
  ModInt &operator/=(const ModInt &p) {
    *this *= p.inverse();
    return *this;
  }
  ModInt &operator^=(long long p) {
    ModInt res = 1;
    for (; p; p >>= 1) {
      if (p & 1)
        res *= *this;
      *this *= *this;
    }
    return *this = res;
  }
  ModInt operator-() const { return ModInt(-x); }
  ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }
  ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }
  ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }
  ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }
  ModInt operator^(long long p) const { return ModInt(*this) ^= p; }
  bool operator==(const ModInt &p) const { return x == p.x; }
  bool operator!=(const ModInt &p) const { return x != p.x; }
  explicit operator int() const { return x; } // added by QCFium
  ModInt operator=(const int p) {
    x = p;
    return ModInt(*this);
  } // added by QCFium
  ModInt inverse() const {
    int a = x, b = mod, u = 1, v = 0, t;
    while (b > 0) {
      t = a / b;
      a -= t * b;
      std::swap(a, b);
      u -= t * v;
      std::swap(u, v);
    }
    return ModInt(u);
  }
  friend std::ostream &operator<<(std::ostream &os, const ModInt<mod> &p) {
    return os << p.x;
  }
  friend std::istream &operator>>(std::istream &is, ModInt<mod> &a) {
    long long x;
    is >> x;
    a = ModInt<mod>(x);
    return (is);
  }
};
typedef ModInt<MOD> mint;

struct MComb {
  std::vector<mint> fact;
  std::vector<mint> inv;
  MComb(int n) { // O(n + log(mod))
    fact = std::vector<mint>(n + 1, 1);
    for (int i = 1; i <= n; i++)
      fact[i] = fact[i - 1] * mint(i);
    inv.resize(n + 1);
    inv[n] = fact[n] ^ (MOD - 2);
    for (int i = n; i--;)
      inv[i] = inv[i + 1] * mint(i + 1);
  }
  mint ncr(int n, int r) { return fact[n] * inv[r] * inv[n - r]; }
  mint npr(int n, int r) { return fact[n] * inv[n - r]; }
  mint nhr(int n, int r) {
    assert(n + r - 1 < (int)fact.size());
    return ncr(n + r - 1, r);
  }
};

int64_t gcd(int64_t a, int64_t b) {
  a = std::abs(a);
  b = std::abs(b);
  while (a && b) {
    if (a > b)
      a %= b;
    else
      b %= a;
  }
  return a + b;
}

int main() {
  int n = ri();
  std::map<std::pair<int64_t, int64_t>, int> all;
  int cnt00 = 0, cnt01 = 0, cnt10 = 0;
  for (int i = 0; i < n; i++) {
    int64_t a, b;
    scanf("%" SCNd64 "%" SCNd64, &a, &b);
    if (a < 0)
      a = -a, b = -b;
    int64_t tmp = gcd(a, b);
    if (tmp)
      a /= tmp, b /= tmp;
    if (!a && !b)
      cnt00++;
    else if (!a)
      cnt01++;
    else if (!b)
      cnt10++;
    else
      all[{a, b}]++;
  }
  mint res = (mint(2) ^ cnt01) + (mint(2) ^ cnt10) - 1;
  while (all.size()) {
    int64_t xx = all.begin()->first.second, yy = -all.begin()->first.first;
    if (xx < 0)
      xx = -xx, yy = -yy;
    auto itr = all.find({xx, yy});
    if (itr == all.end())
      res *= mint(2) ^ all.begin()->second;
    else
      res *= (mint(2) ^ all.begin()->second) + (mint(2) ^ itr->second) - 1,
          all.erase(itr);
    all.erase(all.begin());
  }
  std::cout << res + cnt00 - 1 << std::endl;
  return 0;
}


Error: 0

Fixed submission:

#include <bits/stdc++.h>

int ri() {
  int n;
  scanf("%d", &n);
  return n;
}
#define MOD 1000000007

template <int mod> struct ModInt {
  int x;
  ModInt() : x(0) {}
  ModInt(long long y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
  ModInt &operator+=(const ModInt &p) {
    if ((x += p.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator-=(const ModInt &p) {
    if ((x += mod - p.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator*=(const ModInt &p) {
    x = (int)(1LL * x * p.x % mod);
    return *this;
  }
  ModInt &operator/=(const ModInt &p) {
    *this *= p.inverse();
    return *this;
  }
  ModInt &operator^=(long long p) {
    ModInt res = 1;
    for (; p; p >>= 1) {
      if (p & 1)
        res *= *this;
      *this *= *this;
    }
    return *this = res;
  }
  ModInt operator-() const { return ModInt(-x); }
  ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }
  ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }
  ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }
  ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }
  ModInt operator^(long long p) const { return ModInt(*this) ^= p; }
  bool operator==(const ModInt &p) const { return x == p.x; }
  bool operator!=(const ModInt &p) const { return x != p.x; }
  explicit operator int() const { return x; } // added by QCFium
  ModInt operator=(const int p) {
    x = p;
    return ModInt(*this);
  } // added by QCFium
  ModInt inverse() const {
    int a = x, b = mod, u = 1, v = 0, t;
    while (b > 0) {
      t = a / b;
      a -= t * b;
      std::swap(a, b);
      u -= t * v;
      std::swap(u, v);
    }
    return ModInt(u);
  }
  friend std::ostream &operator<<(std::ostream &os, const ModInt<mod> &p) {
    return os << p.x;
  }
  friend std::istream &operator>>(std::istream &is, ModInt<mod> &a) {
    long long x;
    is >> x;
    a = ModInt<mod>(x);
    return (is);
  }
};
typedef ModInt<MOD> mint;

struct MComb {
  std::vector<mint> fact;
  std::vector<mint> inv;
  MComb(int n) { // O(n + log(mod))
    fact = std::vector<mint>(n + 1, 1);
    for (int i = 1; i <= n; i++)
      fact[i] = fact[i - 1] * mint(i);
    inv.resize(n + 1);
    inv[n] = fact[n] ^ (MOD - 2);
    for (int i = n; i--;)
      inv[i] = inv[i + 1] * mint(i + 1);
  }
  mint ncr(int n, int r) { return fact[n] * inv[r] * inv[n - r]; }
  mint npr(int n, int r) { return fact[n] * inv[n - r]; }
  mint nhr(int n, int r) {
    assert(n + r - 1 < (int)fact.size());
    return ncr(n + r - 1, r);
  }
};

int64_t gcd(int64_t a, int64_t b) {
  a = std::abs(a);
  b = std::abs(b);
  while (a && b) {
    if (a > b)
      a %= b;
    else
      b %= a;
  }
  return a + b;
}

int main() {
  int n = ri();
  std::map<std::pair<int64_t, int64_t>, int> all;
  int cnt00 = 0, cnt01 = 0, cnt10 = 0;
  for (int i = 0; i < n; i++) {
    int64_t a, b;
    scanf("%" SCNd64 "%" SCNd64, &a, &b);
    if (a < 0)
      a = -a, b = -b;
    int64_t tmp = gcd(a, b);
    a /= tmp;
    b /= tmp;
    if (!a && !b)
      cnt00++;
    else if (!a)
      cnt01++;
    else if (!b)
      cnt10++;
    else
      all[{a, b}]++;
  }
  mint res = mint(!!cnt00) + (mint(2) ^ cnt01) + (mint(2) ^ cnt10) - 1;
  while (all.size()) {
    int64_t xx = all.begin()->first.second, yy = -all.begin()->first.first;
    if (xx < 0)
      xx = -xx, yy = -yy;
    auto itr = all.find({xx, yy});
    if (itr == all.end())
      res *= mint(2) ^ all.begin()->second;
    else
      res *= (mint(2) ^ all.begin()->second) + (mint(2) ^ itr->second) - 1,
          all.erase(itr);
    all.erase(all.begin());
  }
  std::cout << res - 1 << std::endl;
  return 0;
}