Problem p02609 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
using namespace std;
using ll = long long;

ll mod;
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; }

#define rep(i, n) for (int i = 0; i < (int)(n); i++)

ll modpow(ll a, ll n, ll m) {
  ll result = 1;

  while (n > 0) {
    if (n & 1)
      result = result * a % m;
    a = a * a % m;
    n >>= 1;
  }
  return result;
}

int f(int n, int count) {
  if (n == 0)
    return count;
  return f(n % __builtin_popcount(n), count + 1);
}

mint getrem(string X, ll icount) {
  mint rem = 0;
  for (int i = 0; i < X.size(); i++) {
    if (X[i] == '1') {
      rem += modpow(2, X.size() - i - 1, icount);
    }
  }
  return rem;
}

int main() {
  string X;
  int N;
  cin >> N >> X;

  ll icount = 0;

  rep(i, N) {
    if (X.at(i) == '1')
      icount++;
  }

  mod = icount - 1;
  if (mod == 0)
    mod = 1; // foo
  mint lessrem = mod > 0 ? getrem(X, mod) : 0;
  mod = icount + 1;
  mint morerem = getrem(X, icount + 1);

  rep(i, N) {
    mod = 1; // foo
    mint rem;
    if (X.at(i) == '1') {
      rem = lessrem;
      mod = icount - 1;
      if (mod == 0) {
        cout << 0 << endl;
        continue;
      }
      rem -= modpow(2, X.size() - i - 1, mod);
    } else {
      rem = morerem;
      mod = icount + 1;
      rem += modpow(2, X.size() - i - 1, mod);
    }

    cout << f(rem.x, 0) + 1 << endl;
  }

  return 0;
}


Error: 0

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
using ll = long long;

ll mod;
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; }

#define rep(i, n) for (int i = 0; i < (int)(n); i++)

ll modpow(ll a, ll n, ll m) {
  ll result = 1;

  while (n > 0) {
    if (n & 1)
      result = result * a % m;
    a = a * a % m;
    n >>= 1;
  }
  return result;
}

int f(int n, int count) {
  if (n == 0)
    return count;
  return f(n % __builtin_popcount(n), count + 1);
}

mint getrem(string X, ll icount) {
  mint rem = 0;
  for (int i = 0; i < X.size(); i++) {
    if (X[i] == '1') {
      rem += modpow(2, X.size() - i - 1, icount);
    }
  }
  return rem;
}

int main() {
  string X;
  int N;
  cin >> N >> X;

  ll icount = 0;

  rep(i, N) {
    if (X.at(i) == '1')
      icount++;
  }

  mod = icount - 1;
  if (mod == 0)
    mod = 9; // foo
  mint lessrem = mod > 0 ? getrem(X, icount - 1) : 0;
  mod = icount + 1;
  mint morerem = getrem(X, icount + 1);

  rep(i, N) {
    mint rem;
    if (X.at(i) == '1') {
      rem = lessrem;
      mod = icount - 1;
      if (mod == 0) {
        cout << 0 << endl;
        continue;
      }
      rem -= modpow(2, X.size() - i - 1, mod);
    } else {
      rem = morerem;
      mod = icount + 1;
      rem += modpow(2, X.size() - i - 1, mod);
    }

    cout << f(rem.x, 0) + 1 << endl;
  }

  return 0;
}