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

#include <bits/stdc++.h>
#ifdef __DEBUG__
#define DBG(X) cout << #X << " = " << (X) << endl;
#define SAY(X) cout << (X) << endl;
#else
#define DBG(X)
#define SAY(X)
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

int dx[] = {1, 0, -1, 0, 1, -1, 1, -1};
int dy[] = {0, 1, 0, -1, 1, 1, -1, -1};
const int INT_INF = (int)(2e9);
const ll LL_INF = (ll)(2e18);

inline void fast_io() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
};
template <typename T, typename S>
inline ostream &operator<<(ostream &os, const pair<T, S> p) {
  cout << "[" << p.first << ";" << p.second << "]";
  return os;
}
template <typename T, typename S>
inline ostream &operator<<(ostream &os, const map<T, S> p) {
  for (auto el : p)
    cout << "[" << el.first << ";" << el.second << "]";
  return os;
}
template <typename T>
inline ostream &operator<<(ostream &os, const vector<T> &v) {
  for (auto el : v)
    cout << el << " ";
  return os;
}
template <typename T>
inline ostream &operator<<(ostream &os, const deque<T> &v) {
  for (auto el : v)
    cout << el << " ";
  return os;
}
template <typename T> inline ostream &operator<<(ostream &os, const set<T> &v) {
  for (auto el : v)
    cout << el << " ";
  return os;
}
template <typename T> inline vector<T> fetch_vec(int sz) {
  vector<T> ret(sz);
  for (auto &elem : ret)
    cin >> elem;
  return ret;
}

template <int mod> struct ModInt {
  int x;

  ModInt() : x(0) {}

  ModInt(int64_t 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-() 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; }

  bool operator==(const ModInt &p) const { return x == p.x; }

  bool operator!=(const ModInt &p) const { return x != p.x; }

  ModInt inverse() const {
    int a = x, b = mod, u = 1, v = 0, t;
    while (b > 0) {
      t = a / b;
      swap(a -= t * b, b);
      swap(u -= t * v, v);
    }
    return ModInt(u);
  }

  ModInt pow(int64_t n) const {
    ModInt ret(1), mul(x);
    while (n > 0) {
      if (n & 1)
        ret *= mul;
      mul *= mul;
      n >>= 1;
    }
    return ret;
  }

  friend ostream &operator<<(ostream &os, const ModInt &p) { return os << p.x; }

  friend istream &operator>>(istream &is, ModInt &a) {
    int64_t t;
    is >> t;
    a = ModInt<mod>(t);
    return (is);
  }

  static int get_mod() { return mod; }
};

const ll mod = 1e9 + 7;
using modint = ModInt<mod>;

int N;
modint cnt0(0);

void normalize(ll &a, ll &b) {
  if (a == 0 && b == 0) {
    cnt0 += 1;
  } else if (a == 0) {
    b = 1;
  } else if (b == 0) {
    a = 1;
  } else {
    if (a < 0) {
      a = -a, b = -b;
    }
    ll d = gcd(a, b);
    a /= d;
    b /= d;
  }
}

unordered_map<ll, unordered_map<ll, int>> cnt;
set<pll> se;
void input() {
  fast_io();
  cin >> N;
  for (int i = 0; i < N; i++) {
    ll a, b;
    cin >> a >> b;
    normalize(a, b);
    cnt[a][b]++;
    se.emplace(a, b);
  }
}

int solve() {
  modint ans(1);
  unordered_map<ll, unordered_map<ll, bool>> used;
  used[0][0] = true;
  for (auto itr = se.begin(); itr != se.end(); ++itr) {
    ll a = itr->first;
    ll b = itr->second;
    if (used[a][b])
      continue;
    modint ret(0);
    ret += modint(2).pow(cnt[a][b]) - 1;
    used[a][b] = true;
    if (b <= 0) {
      ret += modint(2).pow(cnt[-b][a]) - 1;
      used[-b][a] = true;
    } else {
      ret += modint(2).pow(cnt[b][-a]) - 1;
      used[b][-a] = true;
    }
    ret += 1;
    ans *= ret;
  }
  cout << (ans - 1 + cnt0) << endl;
  return 0;
}

int main() {
  input();
  solve();
  return 0;
}

Error: WA

Fixed submission:

#include <bits/stdc++.h>
#ifdef __DEBUG__
#define DBG(X) cout << #X << " = " << (X) << endl;
#define SAY(X) cout << (X) << endl;
#else
#define DBG(X)
#define SAY(X)
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

int dx[] = {1, 0, -1, 0, 1, -1, 1, -1};
int dy[] = {0, 1, 0, -1, 1, 1, -1, -1};
const int INT_INF = (int)(2e9);
const ll LL_INF = (ll)(2e18);

inline void fast_io() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
};
template <typename T, typename S>
inline ostream &operator<<(ostream &os, const pair<T, S> p) {
  cout << "[" << p.first << ";" << p.second << "]";
  return os;
}
template <typename T, typename S>
inline ostream &operator<<(ostream &os, const map<T, S> p) {
  for (auto el : p)
    cout << "[" << el.first << ";" << el.second << "]";
  return os;
}
template <typename T>
inline ostream &operator<<(ostream &os, const vector<T> &v) {
  for (auto el : v)
    cout << el << " ";
  return os;
}
template <typename T>
inline ostream &operator<<(ostream &os, const deque<T> &v) {
  for (auto el : v)
    cout << el << " ";
  return os;
}
template <typename T> inline ostream &operator<<(ostream &os, const set<T> &v) {
  for (auto el : v)
    cout << el << " ";
  return os;
}
template <typename T> inline vector<T> fetch_vec(int sz) {
  vector<T> ret(sz);
  for (auto &elem : ret)
    cin >> elem;
  return ret;
}

template <int mod> struct ModInt {
  int x;

  ModInt() : x(0) {}

  ModInt(int64_t 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-() 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; }

  bool operator==(const ModInt &p) const { return x == p.x; }

  bool operator!=(const ModInt &p) const { return x != p.x; }

  ModInt inverse() const {
    int a = x, b = mod, u = 1, v = 0, t;
    while (b > 0) {
      t = a / b;
      swap(a -= t * b, b);
      swap(u -= t * v, v);
    }
    return ModInt(u);
  }

  ModInt pow(int64_t n) const {
    ModInt ret(1), mul(x);
    while (n > 0) {
      if (n & 1)
        ret *= mul;
      mul *= mul;
      n >>= 1;
    }
    return ret;
  }

  friend ostream &operator<<(ostream &os, const ModInt &p) { return os << p.x; }

  friend istream &operator>>(istream &is, ModInt &a) {
    int64_t t;
    is >> t;
    a = ModInt<mod>(t);
    return (is);
  }

  static int get_mod() { return mod; }
};
const ll mod = 1e9 + 7;
using modint = ModInt<mod>;

template <typename Monoid> struct SegmentTree {
  using F = function<Monoid(Monoid, Monoid)>;

  int sz;
  vector<Monoid> seg;

  const F f;
  const Monoid M1;

  SegmentTree(int n, const F f, const Monoid &M1) : f(f), M1(M1) {
    sz = 1;
    while (sz < n)
      sz <<= 1;
    seg.assign(2 * sz, M1);
  }

  void set(int k, const Monoid &x) { seg[k + sz] = x; }

  void build() {
    for (int k = sz - 1; k > 0; k--) {
      seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
    }
  }

  void update(int k, const Monoid &x) {
    k += sz;
    seg[k] = x;
    while (k >>= 1) {
      seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
    }
  }

  Monoid query(int a, int b) {
    Monoid L = M1, R = M1;
    for (a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
      if (a & 1)
        L = f(L, seg[a++]);
      if (b & 1)
        R = f(seg[--b], R);
    }
    return f(L, R);
  }

  Monoid operator[](const int &k) const { return seg[k + sz]; }

  template <typename C>
  int find_subtree(int a, const C &check, Monoid &M, bool type) {
    while (a < sz) {
      Monoid nxt = type ? f(seg[2 * a + type], M) : f(M, seg[2 * a + type]);
      if (check(nxt))
        a = 2 * a + type;
      else
        M = nxt, a = 2 * a + 1 - type;
    }
    return a - sz;
  }

  template <typename C> int find_first(int a, const C &check) {
    Monoid L = M1;
    if (a <= 0) {
      if (check(f(L, seg[1])))
        return find_subtree(1, check, L, false);
      return -1;
    }
    int b = sz;
    for (a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
      if (a & 1) {
        Monoid nxt = f(L, seg[a]);
        if (check(nxt))
          return find_subtree(a, check, L, false);
        L = nxt;
        ++a;
      }
    }
    return -1;
  }

  template <typename C> int find_last(int b, const C &check) {
    Monoid R = M1;
    if (b >= sz) {
      if (check(f(seg[1], R)))
        return find_subtree(1, check, R, true);
      return -1;
    }
    int a = sz;
    for (b += sz; a < b; a >>= 1, b >>= 1) {
      if (b & 1) {
        Monoid nxt = f(seg[--b], R);
        if (check(nxt))
          return find_subtree(b, check, R, true);
        R = nxt;
      }
    }
    return -1;
  }
};

double eps = 1e-9;
int N;
vector<pair<int, double>> iwashi;
int cnt0;
int cntf0;
void input() {
  fast_io();
  cin >> N;
  cnt0 = 0;
  cntf0 = 0;
  for (size_t i = 0; i < N; i++) {
    ll a, b;
    cin >> a >> b;
    if (a == 0 && b == 0) {
      cnt0++;
      continue;
    }
    if (a == 0) {
      iwashi.emplace_back(0, 1);
      cntf0++;
    } else {
      iwashi.emplace_back(1, (double)b / a);
    }
  }
  sort(iwashi.begin(), iwashi.end());
}

int solve() {
  int N = iwashi.size();
  vector<modint> dp(N, 0);
  DBG(iwashi)
  // modint ans = 0;
  // ans += 1;
  // ans += cnt0;
  dp[0] = 1;
  SegmentTree<modint> seg(
      N + 1, [](modint a, modint b) { return a + b; }, 0);
  seg.update(0, dp[0] + cnt0);
  for (size_t i = 0; i < N; i++) {
    if (iwashi[i].first == 0) {
      dp[i + 1] = seg.query(0, i + 1);
      seg.update(i + 1, dp[i + 1]);
    } else {
      if (abs(iwashi[i].second) == 0) {
        dp[i + 1] = seg.query(cntf0, i + 1);
        seg.update(i + 1, dp[i + 1]);
      } else {
        pair<int, double> tmp = iwashi[i];
        tmp.second = -1.0 / tmp.second;
        auto itrU = upper_bound(iwashi.begin(), iwashi.begin() + i, tmp);
        auto itrL = lower_bound(iwashi.begin(), iwashi.begin() + i, tmp);
        int cnt = itrU - itrL;
        int idxU = itrU - iwashi.begin();
        int idxL = itrL - iwashi.begin();
        // DBG(cnt)
        // ans += modint(2).pow(i-cnt);
        // DBG(ans)
        DBG(idxU)
        DBG(idxL)
        if (idxU == idxL)
          dp[i + 1] = seg.query(0, i + 1);
        else
          dp[i + 1] = seg.query(1, idxL) + seg.query(idxU, i + 1);
        seg.update(i + 1, dp[i + 1]);
      }
    }
    DBG(dp[i + 1])
  }
  cout << seg.query(0, N) << endl;
  return 0;
}

int main() {
  input();
  solve();
  return 0;
}