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

#include "bits/stdc++.h"

#define MOD 1000000007
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define rrep(i, n) for (ll i = (n)-1; i >= 0; i--)
#define ALL(v) v.begin(), v.end()
#define rALL(v) v.rbegin(), v.rend()
#define FOR(i, j, k) for (ll i = j; i < k; i++)
#define DUMP(i, v)                                                             \\
  for (ll i = 0; i < v.size(); i++)                                            \\
  cerr << v[i] << " "

using namespace std;
typedef long long int ll;
typedef vector<ll> llvec;
typedef vector<double> dvec;
typedef pair<ll, ll> P;
typedef long double ld;
struct edge {
  ll x, c;
};

ll mod(ll a, ll mod) {
  ll res = a % mod;
  while (res < 0)
    res = res + mod;
  return res % mod;
}

ll modpow(ll a, ll n, ll modd) {
  ll res = 1;
  while (n > 0) {
    if (n & 1)
      res = res * a % modd;
    a = a * a % modd;
    n >>= 1;
  }
  return mod(res, modd);
}

ll modinv(ll a, ll mod) { return modpow(a, mod - 2, mod); }

ll gcd(ll a, ll b) {
  ll r = a % b;
  if (r == 0)
    return b;
  else
    return gcd(b, a % b);
}

bool is_prime(ll n) {
  ll i = 2;
  if (n == 1)
    return false;
  if (n == 2)
    return true;
  bool res = true;
  while (i * i < n) {
    if (n % i == 0) {
      res = false;
    }
    i = i + 1;
  }

  // if(i==1)res = false;
  if (n % i == 0)
    res = false;
  return res;
}

struct UnionFind {
  ll N;
  llvec p;
  llvec cnt;
  UnionFind(ll n) {
    N = n;
    p = llvec(N);
    cnt = llvec(N, 0);
    rep(i, N) {
      p[i] = i;
      cnt[i] = 1;
    }
  }

  void con(ll a, ll b) {
    P at = root(a);
    P bt = root(b);
    if (at.second != bt.second) {
      if (at.first > bt.first) {
        swap(at, bt);
        swap(a, b);
      }
      p[at.second] = bt.second;
      cnt[bt.second] += cnt[at.second];
      p[a] = bt.second;
    }
  }

  P root(ll a) {
    ll atmp = a;
    ll c = 0;
    while (atmp != p[atmp]) {
      atmp = p[atmp];
      c++;
    }
    p[a] = atmp;
    return {c, atmp};
  }

  bool is_con(ll a, ll b) {
    P at = root(a);
    P bt = root(b);
    return at.second == bt.second;
  }
};

struct dijkstra {
  ll N;
  llvec d;
  vector<vector<edge>> e;
  dijkstra(ll n) {
    N = n;
    // d = llvec(N, 1e18);
    e = vector<vector<edge>>(N);
  }

  void add_edge(ll from, ll to, ll cost) { e[from].push_back({to, cost}); }

  void run(ll start) {
    priority_queue<P, vector<P>, greater<P>> que;
    que.push({0, start});
    d = llvec(N, 1e18);
    d[start] = 0;
    while (!que.empty()) {
      P q = que.top();
      que.pop();
      ll dc = q.first;
      ll x = q.second;
      if (dc > d[x]) {
        continue;
      } else {
        for (auto ip : e[x]) {
          if (d[ip.x] <= d[x] + ip.c) {
            continue;
          } else {
            d[ip.x] = d[x] + ip.c;
            que.push({d[ip.x], ip.x});
          }
        }
      }
    }
  }
};

ll frac[100100];
ll ifrac[100100];

void gen() {
  frac[0] = 1;
  ifrac[0] = 1;
  rep(i, 100099) {
    frac[i + 1] = mod(frac[i] * (i + 1), MOD);
    ifrac[i + 1] = modinv(frac[i + 1], MOD);
  }
}

ll comb(ll n, ll k) {
  ll ans = mod(frac[n] * ifrac[k], MOD);
  ans = mod(ans * ifrac[n - k], MOD);
  return ans;
}

/**************************************
** A main function starts from here  **
***************************************/
int main() {
  ll N;
  cin >> N;
  vector<P> f;
  // map<P, ll> a_b, b_a;
  map<P, ll> a_b, b_a;
  ll fail = 0;
  rep(i, N) {
    ll a, b;
    cin >> a >> b;
    if (a == 0 and b == 0) {
      fail++;
      continue;
    }
    ll ab = abs(a);
    ll bb = abs(b);
    if (ab * bb != 0) {
      ll aaa = gcd(ab, bb);
      a /= aaa;
      b /= aaa;
    } else if (a == 0) {
      b = 1;
    } else if (b == 0) {
      a = 1;
    }
    if (a < 0) {
      a = -a;
      b = -b;
    }
    a_b[{a, b}]++;

    if (-b < 0) {
      b = -b;
      a = -a;
    }
    b_a[{-b, a}]++;
  }
  // N = N-fail;
  ll ans = 1;
  set<P> done;
  for (auto imp : a_b) {
    P p = imp.first;
    if (done.count(p) > 0)
      continue;
    ll a = imp.second;
    ll b = b_a[imp.first];

    /*
    if(p.first==0){
      p.second =-1;
      }
      if(p.second==0){
      p.first =1;
      }
    */
    if (-p.second < 0) {
      p.first = -p.first;
      p.second = -p.second;
    }
    done.insert({-p.second, p.first});
    a = mod(modpow(2, a, MOD) - 1, MOD);
    b = mod(modpow(2, b, MOD) - 1, MOD);
    ans = mod(ans * mod(a + b + 1, MOD), MOD);
  }
  ans = mod(ans + fail, MOD);
  cout << mod(ans - 1, MOD);
  return 0;
}


Error: WA

Fixed submission:

#include "bits/stdc++.h"

#define MOD 1000000007
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define rrep(i, n) for (ll i = (n)-1; i >= 0; i--)
#define ALL(v) v.begin(), v.end()
#define rALL(v) v.rbegin(), v.rend()
#define FOR(i, j, k) for (ll i = j; i < k; i++)
#define DUMP(i, v)                                                             \\
  for (ll i = 0; i < v.size(); i++)                                            \\
  cerr << v[i] << " "

using namespace std;
typedef long long int ll;
typedef vector<ll> llvec;
typedef vector<double> dvec;
typedef pair<ll, ll> P;
typedef long double ld;
struct edge {
  ll x, c;
};

ll mod(ll a, ll mod) {
  ll res = a % mod;
  while (res < 0)
    res = res + mod;
  return res % mod;
}

ll modpow(ll a, ll n, ll modd) {
  ll res = 1;
  while (n > 0) {
    if (n & 1)
      res = res * a % modd;
    a = a * a % modd;
    n >>= 1;
  }
  return mod(res, modd);
}

ll modinv(ll a, ll mod) { return modpow(a, mod - 2, mod); }

ll gcd(ll a, ll b) {
  ll r = a % b;
  if (r == 0)
    return b;
  else
    return gcd(b, a % b);
}

bool is_prime(ll n) {
  ll i = 2;
  if (n == 1)
    return false;
  if (n == 2)
    return true;
  bool res = true;
  while (i * i < n) {
    if (n % i == 0) {
      res = false;
    }
    i = i + 1;
  }

  // if(i==1)res = false;
  if (n % i == 0)
    res = false;
  return res;
}

struct UnionFind {
  ll N;
  llvec p;
  llvec cnt;
  UnionFind(ll n) {
    N = n;
    p = llvec(N);
    cnt = llvec(N, 0);
    rep(i, N) {
      p[i] = i;
      cnt[i] = 1;
    }
  }

  void con(ll a, ll b) {
    P at = root(a);
    P bt = root(b);
    if (at.second != bt.second) {
      if (at.first > bt.first) {
        swap(at, bt);
        swap(a, b);
      }
      p[at.second] = bt.second;
      cnt[bt.second] += cnt[at.second];
      p[a] = bt.second;
    }
  }

  P root(ll a) {
    ll atmp = a;
    ll c = 0;
    while (atmp != p[atmp]) {
      atmp = p[atmp];
      c++;
    }
    p[a] = atmp;
    return {c, atmp};
  }

  bool is_con(ll a, ll b) {
    P at = root(a);
    P bt = root(b);
    return at.second == bt.second;
  }
};

struct dijkstra {
  ll N;
  llvec d;
  vector<vector<edge>> e;
  dijkstra(ll n) {
    N = n;
    // d = llvec(N, 1e18);
    e = vector<vector<edge>>(N);
  }

  void add_edge(ll from, ll to, ll cost) { e[from].push_back({to, cost}); }

  void run(ll start) {
    priority_queue<P, vector<P>, greater<P>> que;
    que.push({0, start});
    d = llvec(N, 1e18);
    d[start] = 0;
    while (!que.empty()) {
      P q = que.top();
      que.pop();
      ll dc = q.first;
      ll x = q.second;
      if (dc > d[x]) {
        continue;
      } else {
        for (auto ip : e[x]) {
          if (d[ip.x] <= d[x] + ip.c) {
            continue;
          } else {
            d[ip.x] = d[x] + ip.c;
            que.push({d[ip.x], ip.x});
          }
        }
      }
    }
  }
};

ll frac[100100];
ll ifrac[100100];

void gen() {
  frac[0] = 1;
  ifrac[0] = 1;
  rep(i, 100099) {
    frac[i + 1] = mod(frac[i] * (i + 1), MOD);
    ifrac[i + 1] = modinv(frac[i + 1], MOD);
  }
}

ll comb(ll n, ll k) {
  ll ans = mod(frac[n] * ifrac[k], MOD);
  ans = mod(ans * ifrac[n - k], MOD);
  return ans;
}

/**************************************
** A main function starts from here  **
***************************************/
int main() {
  ll N;
  cin >> N;
  vector<P> f;
  // map<P, ll> a_b, b_a;
  map<P, ll> a_b, b_a;
  ll fail = 0;
  rep(i, N) {
    ll a, b;
    cin >> a >> b;
    if (a == 0 and b == 0) {
      fail++;
      continue;
    }
    ll ab = abs(a);
    ll bb = abs(b);
    if (ab * bb != 0) {
      ll aaa = gcd(ab, bb);
      a /= aaa;
      b /= aaa;
    } else if (a == 0) {
      b = -1;
    } else if (b == 0) {
      a = 1;
    }
    if (a < 0) {
      a = -a;
      b = -b;
    }
    a_b[{a, b}]++;
    if (-b < 0) {
      b = -b;
      a = -a;
    }
    b_a[{-b, a}]++;
  }
  // N = N-fail;
  ll ans = 1;
  set<P> done;
  for (auto imp : a_b) {
    P p = imp.first;
    if (done.count(p) > 0)
      continue;
    ll a = imp.second;
    ll b = b_a[imp.first];
    // cerr << a <<" " << b << " " <<p.first << " " <<p.second<< endl;
    if (-p.second < 0) {
      p.first *= -1;
      p.second *= -1;
    }
    ll abb = gcd(abs(p.first), abs(p.second));
    done.insert({-p.second / abb, p.first / abb});
    a = mod(modpow(2, a, MOD) - 1, MOD);
    b = mod(modpow(2, b, MOD) - 1, MOD);
    ans = mod(ans * mod(a + b + 1, MOD), MOD);
  }
  ans = mod(ans + fail, MOD);
  cout << mod(ans - 1, MOD);
  return 0;
}