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

/*
confirm 0LL and 1LL
confirm cornercases such as 0
confirm times of cin < 10^6
*/
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using P = pair<ll, ll>;
using Pld = pair<ld, ld>;
using Vec = vector<ll>;
using VecP = vector<P>;
using VecB = vector<bool>;
using VecC = vector<char>;
using VecD = vector<ld>;
using VecS = vector<string>;
using Graph = vector<VecP>;
template <typename T> using Vec1 = vector<T>;
template <typename T> using Vec2 = vector<Vec1<T>>;
#define REP(i, m, n) for (ll i = (m); (i) < (n); ++(i))
#define REPN(i, m, n) for (ll i = (m); (i) <= (n); ++(i))
#define REPR(i, m, n) for (ll i = (m)-1; (i) >= (n); --(i))
#define REPNR(i, m, n) for (ll i = (m); (i) >= (n); --(i))
#define rep(i, n) REP(i, 0, n)
#define repn(i, n) REPN(i, 1, n)
#define repr(i, n) REPR(i, n, 0)
#define repnr(i, n) REPNR(i, n, 1)
#define all(s) (s).begin(), (s).end()
#define pb push_back
#define fs first
#define sc second
template <typename T> bool chmax(T &a, const T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> bool chmin(T &a, const T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> ll pow2(const T n) { return (1LL << n); }
template <typename T> void cosp(const T n) { cout << n << ' '; }
void co(void) { cout << '\\n'; }
template <typename T> void co(const T n) { cout << n << '\\n'; }
template <typename T1, typename T2> void co(pair<T1, T2> p) {
  cout << p.fs << ' ' << p.sc << '\\n';
}
template <typename T> void co(const Vec1<T> &v) {
  for (T i : v)
    cosp(i);
  co();
}
template <typename T> void co(initializer_list<T> v) {
  for (T i : v)
    cosp(i);
  co();
}
template <typename T> void ce(const T n) { cerr << n << endl; }
void sonic() {
  ios::sync_with_stdio(false);
  cin.tie(0);
}
void setp(const ll n) { cout << fixed << setprecision(n); }
constexpr int INF = 1e9 + 1;
constexpr ll LINF = 1e18 + 1;
constexpr ll MOD = 1e9 + 7;
// constexpr ll MOD = 998244353;
constexpr ld EPS = 1e-11;
const ld PI = acos(-1);

ll gcd(ll a, ll b) {
  if (!b)
    return abs(a);
  return gcd(b, a % b);
}

ll PowMod(ll a, ll n) {
  if (n < 0)
    return PowMod(PowMod(a, -n), MOD - 2);
  if (n == 0)
    return 1;
  if (n == 1)
    return a;
  if (n % 2 == 0)
    return PowMod(a * a % MOD, n / 2);
  return a * PowMod(a * a % MOD, n / 2) % MOD;
}

ll inv(ll a) { return PowMod(a, MOD - 2); }

int main(void) {
  ll n;
  cin >> n;
  Vec a(n), b(n);
  rep(i, n) cin >> a[i] >> b[i];

  rep(i, n) {
    ll g = gcd(a[i], b[i]);
    if (!g)
      continue;
    if (b[i] < 0)
      g = -g;
    if (b[i] == 0)
      g = a[i];
    a[i] /= g;
    b[i] /= g;
  }

  ll cnt = 0;
  map<P, P> mp;
  rep(i, n) {
    if (a[i] == 0 && b[i] == 0) {
      cnt++;
      continue;
    }
    if (a[i] > 0)
      mp[{a[i], b[i]}].fs++;
    else
      mp[{b[i], -a[i]}].sc++;
  }

  ll ans = 1;
  for (auto p : mp) {
    // co(p.fs);
    // co(p.sc);
    (ans *= PowMod(2, p.sc.fs) + PowMod(2, p.sc.sc) - 1) %= MOD;
    // co(ans);
  }
  co((ans - 1 + cnt + MOD) % MOD);

  return 0;
}


Error: 0
0 2
0 4
1 6


Fixed submission:

/*
confirm 0LL and 1LL
confirm cornercases such as 0
confirm times of cin < 10^6
*/
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using P = pair<ll, ll>;
using Pld = pair<ld, ld>;
using Vec = vector<ll>;
using VecP = vector<P>;
using VecB = vector<bool>;
using VecC = vector<char>;
using VecD = vector<ld>;
using VecS = vector<string>;
using Graph = vector<VecP>;
template <typename T> using Vec1 = vector<T>;
template <typename T> using Vec2 = vector<Vec1<T>>;
#define REP(i, m, n) for (ll i = (m); (i) < (n); ++(i))
#define REPN(i, m, n) for (ll i = (m); (i) <= (n); ++(i))
#define REPR(i, m, n) for (ll i = (m)-1; (i) >= (n); --(i))
#define REPNR(i, m, n) for (ll i = (m); (i) >= (n); --(i))
#define rep(i, n) REP(i, 0, n)
#define repn(i, n) REPN(i, 1, n)
#define repr(i, n) REPR(i, n, 0)
#define repnr(i, n) REPNR(i, n, 1)
#define all(s) (s).begin(), (s).end()
#define pb push_back
#define fs first
#define sc second
template <typename T> bool chmax(T &a, const T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> bool chmin(T &a, const T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> ll pow2(const T n) { return (1LL << n); }
template <typename T> void cosp(const T n) { cout << n << ' '; }
void co(void) { cout << '\\n'; }
template <typename T> void co(const T n) { cout << n << '\\n'; }
template <typename T1, typename T2> void co(pair<T1, T2> p) {
  cout << p.fs << ' ' << p.sc << '\\n';
}
template <typename T> void co(const Vec1<T> &v) {
  for (T i : v)
    cosp(i);
  co();
}
template <typename T> void co(initializer_list<T> v) {
  for (T i : v)
    cosp(i);
  co();
}
template <typename T> void ce(const T n) { cerr << n << endl; }
void sonic() {
  ios::sync_with_stdio(false);
  cin.tie(0);
}
void setp(const ll n) { cout << fixed << setprecision(n); }
constexpr int INF = 1e9 + 1;
constexpr ll LINF = 1e18 + 1;
constexpr ll MOD = 1e9 + 7;
// constexpr ll MOD = 998244353;
constexpr ld EPS = 1e-11;
const ld PI = acos(-1);

ll gcd(ll a, ll b) {
  if (!b)
    return a;
  return gcd(b, a % b);
}

ll PowMod(ll a, ll n) {
  if (n < 0)
    return PowMod(PowMod(a, -n), MOD - 2);
  if (n == 0)
    return 1;
  if (n == 1)
    return a;
  if (n % 2 == 0)
    return PowMod(a * a % MOD, n / 2);
  return a * PowMod(a * a % MOD, n / 2) % MOD;
}

int main(void) {
  ll n;
  cin >> n;
  Vec a(n), b(n);
  rep(i, n) cin >> a[i] >> b[i];
  rep(i, n) {
    ll g = gcd(a[i], b[i]);
    a[i] /= g;
    b[i] /= g;
  }

  map<P, ll> plus, minus;
  ll cntA = 0, cntB = 0, cntZ = 0;
  ll ans = 1;
  rep(i, n) {
    ll ng = cntZ;
    ll absA = abs(a[i]), absB = abs(b[i]);
    if (a[i] * b[i] > 0) {
      ng += minus[{absB, absA}];
      plus[{absA, absB}]++;
    } else if (a[i] * b[i] < 0) {
      ng += plus[{absB, absA}];
      minus[{absA, absB}]++;
    } else {
      if (a[i] == 0 && b[i] == 0) {
        ng += cntA + cntB + plus.size() + minus.size();
        cntZ++;
      } else if (a[i] == 0) {
        ng += cntB;
        cntA++;
      } else {
        ng += cntA;
        cntB++;
      }
    }
    if (ng == 0)
      ans *= 2;
    else
      ans += ans / PowMod(2, ng);
    ans %= MOD;
    cerr << ng << " " << ans << endl;
  }
  co(ans - 1);

  return 0;
}