Problem p02653 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
using namespace std;
#define LOCAL
#pragma region Macros
typedef long long ll;
#define ALL(x) (x).begin(), (x).end()
const long long MOD = 1e9 + 7;
// const long long MOD=998244353;
const int INF = 1e9;
const long long IINF = 1e18;
const int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const char dir[4] = {'D', 'R', 'U', 'L'};

template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &x : v)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < v.size(); ++i) {
    os << v[i] << (i + 1 == v.size() ? "" : " ");
  }
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  cout << '(' << p.first << ',' << p.second << ')';
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const map<T, U> &m) {
  os << '{';
  for (auto itr = m.begin(); itr != m.end(); ++itr) {
    os << '(' << itr->first << ',' << itr->second << ')';
    if (++itr != m.end())
      os << ',';
    --itr;
  }
  os << '}';
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const set<T> &s) {
  os << '{';
  for (auto itr = s.begin(); itr != s.end(); ++itr) {
    os << *itr;
    if (++itr != s.end())
      os << ',';
    --itr;
  }
  os << '}';
  return os;
}

void debug_out() { cerr << '\\n'; }
template <class Head, class... Tail>
void debug_out(Head &&head, Tail &&...tail) {
  cerr << head;
  if (sizeof...(Tail) > 0)
    cerr << ", ";
  debug_out(move(tail)...);
}
#ifdef LOCAL
#define debug(...)                                                             \\
  cerr << " ";                                                                 \\
  cerr << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]"      \\
       << '\\n';                                                                \\
  cerr << " ";                                                                 \\
  debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

template <typename T> T gcd(T x, T y) { return y != 0 ? gcd(y, x % y) : x; }
template <typename T> T lcm(T x, T y) { return x / gcd(x, y) * y; }

template <class T1, class T2> inline bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T1, class T2> inline bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
#pragma endregion

template <uint_fast64_t Modulus> class modint {
  using u64 = uint_fast64_t;

public:
  u64 a;
  constexpr modint(const u64 x = 0) noexcept : a(x % Modulus) {}
  constexpr u64 &value() noexcept { return a; }
  constexpr const u64 &value() const noexcept { return a; }
  constexpr modint &operator+=(const modint &rhs) noexcept {
    a += rhs.a;
    if (a >= Modulus)
      a -= Modulus;
    return *this;
  }
  constexpr modint operator+(const modint &rhs) const noexcept {
    return modint(*this) += rhs;
  }
  constexpr modint &operator++() noexcept { return ++a, *this; }
  constexpr modint operator++(int) noexcept {
    modint t = *this;
    return ++a, t;
  }
  constexpr modint &operator-=(const modint &rhs) noexcept {
    if (a < rhs.a)
      a += Modulus;
    a -= rhs.a;
    return *this;
  }
  constexpr modint operator-(const modint &rhs) const noexcept {
    return modint(*this) -= rhs;
  }
  constexpr modint &operator--() noexcept { return --a, *this; }
  constexpr modint operator--(int) noexcept {
    modint t = *this;
    return --a, t;
  }
  constexpr modint &operator*=(const modint &rhs) noexcept {
    a = a * rhs.a % Modulus;
    return *this;
  }
  constexpr modint operator*(const modint &rhs) const noexcept {
    return modint(*this) *= rhs;
  }
  constexpr modint &operator/=(modint rhs) noexcept {
    u64 exp = Modulus - 2;
    while (exp) {
      if (exp & 1)
        *this *= rhs;
      rhs *= rhs;
      exp >>= 1;
    }
    return *this;
  }
  constexpr modint operator/(const modint &rhs) const noexcept {
    return modint(*this) /= rhs;
  }
  constexpr modint operator-() const noexcept { return modint(Modulus - a); }
  constexpr bool operator==(const modint &rhs) const noexcept {
    return a == rhs.a;
  }
  constexpr bool operator!=(const modint &rhs) const noexcept {
    return a != rhs.a;
  }
  constexpr bool operator!() const noexcept { return !a; }
  friend constexpr modint pow(modint rhs, long long exp) noexcept {
    modint res{1};
    while (exp) {
      if (exp & 1)
        res *= rhs;
      rhs *= rhs;
      exp >>= 1;
    }
    return res;
  }
  template <class T> friend constexpr modint operator+(T x, modint y) noexcept {
    return modint(x) + y;
  }
  template <class T> friend constexpr modint operator-(T x, modint y) noexcept {
    return modint(x) - y;
  }
  template <class T> friend constexpr modint operator*(T x, modint y) noexcept {
    return modint(x) * y;
  }
  template <class T> friend constexpr modint operator/(T x, modint y) noexcept {
    return modint(x) / y;
  }
  friend ostream &operator<<(ostream &s, const modint &rhs) noexcept {
    return s << rhs.a;
  }
  friend istream &operator>>(istream &s, modint &rhs) noexcept {
    u64 a;
    rhs = modint{(s >> a, a)};
    return s;
  }
};

using mint = modint<MOD>;

int brute(int N, int A, int B) {
  int res = 0;
  for (int mask = 0; mask < (1 << N); ++mask) {
    auto d = [&](int i) { return (mask & 1 << i) >> i; };
    vector<pair<int, int>> v;
    int cnt = 1;
    for (int i = 0; i + 1 < N; ++i) {
      if (d(i) != d(i + 1)) {
        v.emplace_back(d(i), cnt);
        cnt = 1;
      } else
        ++cnt;
    }
    v.emplace_back(d(N - 1), cnt);
    for (auto &p : v) {
      if (p.first == 1 && p.second >= B) {
        p.first = 0;
      }
    }
    int now = 0, ok = 0;
    for (auto p : v) {
      if (p.first == 1)
        now = 0;
      else {
        now += p.second;
        if (now >= A)
          ok = 1;
      }
    }
    // debug(mask,ok,v);
    res += ok;
  }
  return res;
}

const int MAX_N = 5010;

mint dp[MAX_N][MAX_N][2];

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int N, A, B;
  cin >> N >> A >> B;
  if (A < B)
    swap(A, B);
  if (B == 1) {
    cout << pow((mint)2, N) << '\\n';
    return 0;
  }
  dp[0][0][0] = 1;
  for (int i = 0; i < N; ++i) {
    for (int j = 0; j < A; ++j) {
      dp[i + 1][j + 1][0] += dp[i][j][0];
      if (j >= B)
        dp[i + 1][j + 1][0] += dp[i][j][1];
      else
        dp[i + 1][1][0] += dp[i][j][1];
      if (j + 1 != B)
        dp[i + 1][j + 1][1] += dp[i][j][1];
      if (i + B <= N)
        dp[i + B][min(A, j + B)][1] += dp[i][j][0];
      dp[i + 1][1][1] += dp[i][j][0];
    }
    /*
    for (int j=0;j<=A;++j) cerr << dp[i+1][j][0] << (j==A?'\\n':' ');
    for (int j=0;j<=A;++j) cerr << dp[i+1][j][1] << (j==A?'\\n':' ');
    cerr << '\\n';
    */
  }
  mint ans = 0, po = 1;
  for (int i = N; i >= 0; --i) {
    ans += (dp[i][A][0] + dp[i][A][1]) * po;
    po *= 2;
  }
  cout << ans << '\\n';
  // cout << brute(N,A,B) << '\\n';
}

Error: -11

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
#define LOCAL
#pragma region Macros
typedef long long ll;
#define ALL(x) (x).begin(), (x).end()
const long long MOD = 1e9 + 7;
// const long long MOD=998244353;
const int INF = 1e9;
const long long IINF = 1e18;
const int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const char dir[4] = {'D', 'R', 'U', 'L'};

template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &x : v)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < v.size(); ++i) {
    os << v[i] << (i + 1 == v.size() ? "" : " ");
  }
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  cout << '(' << p.first << ',' << p.second << ')';
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const map<T, U> &m) {
  os << '{';
  for (auto itr = m.begin(); itr != m.end(); ++itr) {
    os << '(' << itr->first << ',' << itr->second << ')';
    if (++itr != m.end())
      os << ',';
    --itr;
  }
  os << '}';
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const set<T> &s) {
  os << '{';
  for (auto itr = s.begin(); itr != s.end(); ++itr) {
    os << *itr;
    if (++itr != s.end())
      os << ',';
    --itr;
  }
  os << '}';
  return os;
}

void debug_out() { cerr << '\\n'; }
template <class Head, class... Tail>
void debug_out(Head &&head, Tail &&...tail) {
  cerr << head;
  if (sizeof...(Tail) > 0)
    cerr << ", ";
  debug_out(move(tail)...);
}
#ifdef LOCAL
#define debug(...)                                                             \\
  cerr << " ";                                                                 \\
  cerr << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]"      \\
       << '\\n';                                                                \\
  cerr << " ";                                                                 \\
  debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

template <typename T> T gcd(T x, T y) { return y != 0 ? gcd(y, x % y) : x; }
template <typename T> T lcm(T x, T y) { return x / gcd(x, y) * y; }

template <class T1, class T2> inline bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T1, class T2> inline bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
#pragma endregion

template <uint_fast64_t Modulus> class modint {
  using u64 = uint_fast64_t;

public:
  u64 a;
  constexpr modint(const u64 x = 0) noexcept : a(x % Modulus) {}
  constexpr u64 &value() noexcept { return a; }
  constexpr const u64 &value() const noexcept { return a; }
  constexpr modint &operator+=(const modint &rhs) noexcept {
    a += rhs.a;
    if (a >= Modulus)
      a -= Modulus;
    return *this;
  }
  constexpr modint operator+(const modint &rhs) const noexcept {
    return modint(*this) += rhs;
  }
  constexpr modint &operator++() noexcept { return ++a, *this; }
  constexpr modint operator++(int) noexcept {
    modint t = *this;
    return ++a, t;
  }
  constexpr modint &operator-=(const modint &rhs) noexcept {
    if (a < rhs.a)
      a += Modulus;
    a -= rhs.a;
    return *this;
  }
  constexpr modint operator-(const modint &rhs) const noexcept {
    return modint(*this) -= rhs;
  }
  constexpr modint &operator--() noexcept { return --a, *this; }
  constexpr modint operator--(int) noexcept {
    modint t = *this;
    return --a, t;
  }
  constexpr modint &operator*=(const modint &rhs) noexcept {
    a = a * rhs.a % Modulus;
    return *this;
  }
  constexpr modint operator*(const modint &rhs) const noexcept {
    return modint(*this) *= rhs;
  }
  constexpr modint &operator/=(modint rhs) noexcept {
    u64 exp = Modulus - 2;
    while (exp) {
      if (exp & 1)
        *this *= rhs;
      rhs *= rhs;
      exp >>= 1;
    }
    return *this;
  }
  constexpr modint operator/(const modint &rhs) const noexcept {
    return modint(*this) /= rhs;
  }
  constexpr modint operator-() const noexcept { return modint(Modulus - a); }
  constexpr bool operator==(const modint &rhs) const noexcept {
    return a == rhs.a;
  }
  constexpr bool operator!=(const modint &rhs) const noexcept {
    return a != rhs.a;
  }
  constexpr bool operator!() const noexcept { return !a; }
  friend constexpr modint pow(modint rhs, long long exp) noexcept {
    modint res{1};
    while (exp) {
      if (exp & 1)
        res *= rhs;
      rhs *= rhs;
      exp >>= 1;
    }
    return res;
  }
  template <class T> friend constexpr modint operator+(T x, modint y) noexcept {
    return modint(x) + y;
  }
  template <class T> friend constexpr modint operator-(T x, modint y) noexcept {
    return modint(x) - y;
  }
  template <class T> friend constexpr modint operator*(T x, modint y) noexcept {
    return modint(x) * y;
  }
  template <class T> friend constexpr modint operator/(T x, modint y) noexcept {
    return modint(x) / y;
  }
  friend ostream &operator<<(ostream &s, const modint &rhs) noexcept {
    return s << rhs.a;
  }
  friend istream &operator>>(istream &s, modint &rhs) noexcept {
    u64 a;
    rhs = modint{(s >> a, a)};
    return s;
  }
};

using mint = modint<MOD>;

int brute(int N, int A, int B) {
  int res = 0;
  for (int mask = 0; mask < (1 << N); ++mask) {
    auto d = [&](int i) { return (mask & 1 << i) >> i; };
    vector<pair<int, int>> v;
    int cnt = 1;
    for (int i = 0; i + 1 < N; ++i) {
      if (d(i) != d(i + 1)) {
        v.emplace_back(d(i), cnt);
        cnt = 1;
      } else
        ++cnt;
    }
    v.emplace_back(d(N - 1), cnt);
    for (auto &p : v) {
      if (p.first == 1 && p.second >= B) {
        p.first = 0;
      }
    }
    int now = 0, ok = 0;
    for (auto p : v) {
      if (p.first == 1)
        now = 0;
      else {
        now += p.second;
        if (now >= A)
          ok = 1;
      }
    }
    // debug(mask,ok,v);
    res += ok;
  }
  return res;
}

const int MAX_N = 5010;

mint dp[MAX_N][MAX_N][2];

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int N, A, B;
  cin >> N >> A >> B;
  if (A < B)
    swap(A, B);
  dp[0][0][0] = 1;
  for (int i = 0; i < N; ++i) {
    for (int j = 0; j < A; ++j) {
      dp[i + 1][j + 1][0] += dp[i][j][0];
      if (j >= B)
        dp[i + 1][j + 1][0] += dp[i][j][1];
      if (j + 1 != B)
        dp[i + 1][j + 1][1] += dp[i][j][1];
      dp[i + B][min(A, j + B)][1] += dp[i][j][0];
      dp[i + 1][1][1] += dp[i][j][0];
      if (j < B)
        dp[i + 1][1][0] += dp[i][j][1];
    }
    /*
    for (int j=0;j<=A;++j) cerr << dp[i+1][j][0] << (j==B?'\\n':' ');
    for (int j=0;j<=A;++j) cerr << dp[i+1][j][1] << (j==B?'\\n':' ');
    cerr << '\\n';
    */
  }
  mint ans = 0, po = 1;
  for (int i = N; i >= 0; --i) {
    ans += (dp[i][A][0] + dp[i][A][1]) * po;
    po *= 2;
  }
  cout << ans << '\\n';
  // cout << brute(N,A,B) << '\\n';
}