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

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

#define REP(i, m, n) for (int i = (m); i < (int)(n); i++)
#define RREP(i, m, n) for (int i = (int)(n - 1); i >= m; i--)
#define rep(i, n) REP(i, 0, n)
#define rrep(i, n) RREP(i, 0, n)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define fi first
#define se second
#define debug(...)                                                             \\
  {                                                                            \\
    cerr << "[L" << __LINE__ << "] ";                                          \\
    _debug(__VA_ARGS__);                                                       \\
  }

template <typename T> string join(const vector<T> &v, string del = ", ") {
  stringstream s;
  for (auto x : v)
    s << del << x;
  return s.str().substr(del.size());
}
template <typename T> ostream &operator<<(ostream &o, const vector<T> &v) {
  if (v.size())
    o << "[" << join(v) << "]";
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const vector<vector<T>> &vv) {
  int l = vv.size();
  if (l) {
    o << endl;
    rep(i, l) o << (i == 0 ? "[ " : ",\\n  ") << vv[i]
                << (i == l - 1 ? " ]" : "");
  }
  return o;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &o, const pair<T1, T2> &p) {
  return o << "(" << p.first << ", " << p.second << ")";
}
inline void _debug() { cerr << endl; }
template <class First, class... Rest>
void _debug(const First &first, const Rest &...rest) {
  cerr << first << " ";
  _debug(rest...);
}

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;

const double PI = (1 * acos(0.0));
const double EPS = 1e-9;
const int INF = 0x3f3f3f3f;
const ll INFL = 0x3f3f3f3f3f3f3f3fLL;
const ll mod = 1e9 + 7;

inline void finput(string filename) { freopen(filename.c_str(), "r", stdin); }

ll f(ll n) {
  if (n == 0)
    return 0;
  ll bcnt = __builtin_popcountll(n);
  return 1 + f(n % bcnt);
}

ll mod_pow(ll x, ll n, ll m) {
  ll res = 1, a = x;
  for (; n > 0; a = a * a % m, n >>= 1)
    if (n & 1)
      (res *= a) %= m;
  return res;
}

int main() {
  ios_base::sync_with_stdio(0);
  // finput("./input");
  int n;
  cin >> n;
  string s;
  cin >> s;

  int bitcnt = count(s.cbegin(), s.cend(), '1');
  vi modx(2, 0);

  rep(i, n) {
    if (s[i] == '1') {
      rep(j, 2) {
        int d = bitcnt + ((j == 0) ? -1 : 1);
        if (d != 0) {
          modx[j] += mod_pow(2, n - i - 1, d);
          modx[j] %= d;
        }
      }
    }
  }
  rep(i, n) {
    int x, d;
    if (s[i] == '1') {
      x = modx[0];
      d = bitcnt - 1;
      if (d != 0) {
        x += d - mod_pow(2, n - i - 1, d);
        x %= d;
      }
    } else {
      x = modx[1];
      d = bitcnt + 1;
      x += mod_pow(2, n - i - 1, d);
      x %= d;
    }
    if (d == 0)
      cout << 0 << endl;
    else
      cout << f(x) + 1 << endl;
  }
  return 0;
}

Error: 0

Fixed submission:

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

#define REP(i, m, n) for (int i = (m); i < (int)(n); i++)
#define RREP(i, m, n) for (int i = (int)(n - 1); i >= m; i--)
#define rep(i, n) REP(i, 0, n)
#define rrep(i, n) RREP(i, 0, n)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define fi first
#define se second
#define debug(...)                                                             \\
  {                                                                            \\
    cerr << "[L" << __LINE__ << "] ";                                          \\
    _debug(__VA_ARGS__);                                                       \\
  }

template <typename T> string join(const vector<T> &v, string del = ", ") {
  stringstream s;
  for (auto x : v)
    s << del << x;
  return s.str().substr(del.size());
}
template <typename T> ostream &operator<<(ostream &o, const vector<T> &v) {
  if (v.size())
    o << "[" << join(v) << "]";
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const vector<vector<T>> &vv) {
  int l = vv.size();
  if (l) {
    o << endl;
    rep(i, l) o << (i == 0 ? "[ " : ",\\n  ") << vv[i]
                << (i == l - 1 ? " ]" : "");
  }
  return o;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &o, const pair<T1, T2> &p) {
  return o << "(" << p.first << ", " << p.second << ")";
}
inline void _debug() { cerr << endl; }
template <class First, class... Rest>
void _debug(const First &first, const Rest &...rest) {
  cerr << first << " ";
  _debug(rest...);
}

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;

const double PI = (1 * acos(0.0));
const double EPS = 1e-9;
const int INF = 0x3f3f3f3f;
const ll INFL = 0x3f3f3f3f3f3f3f3fLL;
const ll mod = 1e9 + 7;

inline void finput(string filename) { freopen(filename.c_str(), "r", stdin); }

int f(int n) {
  if (n == 0)
    return 0;
  int bcnt = __builtin_popcountll(n);
  return 1 + f(n % bcnt);
}

int main() {
  ios_base::sync_with_stdio(0);
  // finput("./input");
  int n;
  cin >> n;
  string s;
  cin >> s;

  int bitcnt = count(s.cbegin(), s.cend(), '1');
  vi modx(2, 0);

  rep(i, n) {
    if (s[i] == '1') {
      rep(j, 2) {
        int d = bitcnt + ((j == 0) ? -1 : 1);
        if (d != 0) {
          modx[j] += (1 << (n - i - 1)) % d;
          modx[j] %= d;
        }
      }
    }
  }
  rep(i, n) {
    int x, d;
    if (s[i] == '1') {
      x = modx[0];
      d = bitcnt - 1;
      x += d - ((1 << (n - i - 1)) % d);
      x %= d;
    } else {
      x = modx[1];
      d = bitcnt + 1;
      x += (1 << (n - i - 1)) % d;
      x %= d;
    }
    cout << f(x) + 1 << endl;
  }
  return 0;
}