Problem p02733 (C++)

Buggy submission (status: Runtime Error):
// header
#ifdef LOCAL
#include "cxx-prettyprint-master/prettyprint.hpp"
#define debug(x) cout << x << endl
#else
#define debug(...) 42
#endif
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
// types
using namespace std;
using ll = long long;
using ld = long double;
typedef pair<ll, ll> Pl;
typedef pair<int, int> Pi;
typedef vector<ll> vl;
typedef vector<int> vi;
template <typename T> using mat = vector<vector<T>>;
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; }
};
// abreviations
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define rep_(i, a_, b_, a, b, ...)                                             \
  for (int i = (a), max_i = (b); i < max_i; i++)
#define rep(i, ...) rep_(i, __VA_ARGS__, __VA_ARGS__, 0, __VA_ARGS__)
#define rev(i, n) for (int i = n - 1; i >= 0; i--)
#define SZ(x) ((ll)(x).size())
#define pb(x) push_back(x)
#define eb(x) emplace_back(x)
#define ff first
#define ss second
#define mp make_pair
#define print(x) cout << x << endl
// functions
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename T> T mypow(T x, ll n) {
  T ret = 1;
  while (n > 0) {
    if (n & 1)
      (ret *= x);
    (x *= x);
    n >>= 1;
  }
  return ret;
}
ll modpow(ll x, ll n, const ll mod) {
  ll ret = 1;
  while (n > 0) {
    if (n & 1)
      (ret *= x);
    (x *= x);
    n >>= 1;
    x %= mod;
    ret %= mod;
  }
  return ret;
}
uint64_t my_rand(void) {
  static uint64_t x = 88172645463325252ULL;
  x = x ^ (x << 13);
  x = x ^ (x >> 7);
  return x = x ^ (x << 17);
}
// graph template
template <typename T> struct edge {
  int src, to;
  T cost;

  edge(int to, T cost) : src(-1), to(to), cost(cost) {}

  edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}

  edge &operator=(const int &x) {
    to = x;
    return *this;
  }
  operator int() const { return to; }
};

template <typename T> using Edges = vector<edge<T>>;
template <typename T> using WeightedGraph = vector<Edges<T>>;
using UnWeightedGraph = vector<vector<int>>;

// constant
#define INF 1000000000000000LL
#define mod 1000000007LL
typedef modint<mod> mint;
#define eps 0.0000000000008
// library

// main
int main() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cout << fixed << setprecision(20);
  int h, w, k;
  cin >> h >> w >> k;
  mat<int> s(h, vi(w));
  rep(i, h) rep(j, w) {
    char x;
    cin >> x;
    s[i][j] = x - '0';
  }
  mat<int> cumsum(h + 1, vi(w));
  rep(i, h) rep(j, w) cumsum[i][j + 1] = cumsum[i][j] + s[i][j];
  int ans = h + w;
  rep(s, 1 << (h - 1), 1 << h) {
    int now = 0;
    int cnt = 0;
    bool flag = true;
    rep(i, w) {
      int res = 0;
      rep(j, h) {
        res += cumsum[j][i + 1] - cumsum[j][now];
        if ((1 << j) & s) {
          if (res > k) {
            if (now == i)
              flag = false;
            now = i;
            cnt++;
          }
          res = 0;
        }
      }
    }
    if (not flag)
      continue;
    rep(i, h - 1) {
      if ((1 << i) & s)
        cnt++;
    }
    chmin(ans, cnt);
  }
  print(ans);
}

Fixed submission:
// header
#ifdef LOCAL
#include "cxx-prettyprint-master/prettyprint.hpp"
#define debug(x) cout << x << endl
#else
#define debug(...) 42
#endif
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
// types
using namespace std;
using ll = long long;
using ld = long double;
typedef pair<ll, ll> Pl;
typedef pair<int, int> Pi;
typedef vector<ll> vl;
typedef vector<int> vi;
template <typename T> using mat = vector<vector<T>>;
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; }
};
// abreviations
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define rep_(i, a_, b_, a, b, ...)                                             \
  for (int i = (a), max_i = (b); i < max_i; i++)
#define rep(i, ...) rep_(i, __VA_ARGS__, __VA_ARGS__, 0, __VA_ARGS__)
#define rev(i, n) for (int i = n - 1; i >= 0; i--)
#define SZ(x) ((ll)(x).size())
#define pb(x) push_back(x)
#define eb(x) emplace_back(x)
#define ff first
#define ss second
#define mp make_pair
#define print(x) cout << x << endl
// functions
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename T> T mypow(T x, ll n) {
  T ret = 1;
  while (n > 0) {
    if (n & 1)
      (ret *= x);
    (x *= x);
    n >>= 1;
  }
  return ret;
}
ll modpow(ll x, ll n, const ll mod) {
  ll ret = 1;
  while (n > 0) {
    if (n & 1)
      (ret *= x);
    (x *= x);
    n >>= 1;
    x %= mod;
    ret %= mod;
  }
  return ret;
}
uint64_t my_rand(void) {
  static uint64_t x = 88172645463325252ULL;
  x = x ^ (x << 13);
  x = x ^ (x >> 7);
  return x = x ^ (x << 17);
}
// graph template
template <typename T> struct edge {
  int src, to;
  T cost;

  edge(int to, T cost) : src(-1), to(to), cost(cost) {}

  edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}

  edge &operator=(const int &x) {
    to = x;
    return *this;
  }
  operator int() const { return to; }
};

template <typename T> using Edges = vector<edge<T>>;
template <typename T> using WeightedGraph = vector<Edges<T>>;
using UnWeightedGraph = vector<vector<int>>;

// constant
#define INF 1000000000000000LL
#define mod 1000000007LL
typedef modint<mod> mint;
#define eps 0.0000000000008
// library

// main
int main() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cout << fixed << setprecision(20);
  int h, w, k;
  cin >> h >> w >> k;
  mat<int> s(h, vi(w));
  rep(i, h) rep(j, w) {
    char x;
    cin >> x;
    s[i][j] = x - '0';
  }
  mat<int> cumsum(h, vi(w + 1));
  rep(i, h) rep(j, w) cumsum[i][j + 1] = cumsum[i][j] + s[i][j];
  int ans = h + w;
  rep(s, 1 << (h - 1), 1 << h) {
    int now = 0;
    int cnt = 0;
    bool flag = true;
    rep(i, w) {
      int res = 0;
      rep(j, h) {
        res += cumsum[j][i + 1] - cumsum[j][now];
        if ((1 << j) & s) {
          if (res > k) {
            if (now == i)
              flag = false;
            now = i;
            cnt++;
          }
          res = 0;
        }
      }
    }
    if (not flag)
      continue;
    rep(i, h - 1) {
      if ((1 << i) & s)
        cnt++;
    }
    chmin(ans, cnt);
  }
  print(ans);
}