Problem p02549 (C++) — buggy submission, verdict: Time Limit Exceeded

#pragma GCC optimize("Ofast")
#include "bits/stdc++.h"

// Begin Header {{{
using namespace std;

#ifndef DEBUG
#define dump(...)
#endif

#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define rep(i, b, e) for (intmax_t i = (b), i##_limit = (e); i < i##_limit; ++i)
#define repc(i, b, e)                                                          \\
  for (intmax_t i = (b), i##_limit = (e); i <= i##_limit; ++i)
#define repr(i, b, e)                                                          \\
  for (intmax_t i = (b), i##_limit = (e); i >= i##_limit; --i)
#define var(Type, ...)                                                         \\
  Type __VA_ARGS__;                                                            \\
  input(__VA_ARGS__)

constexpr size_t operator""_zu(unsigned long long value) { return value; };
constexpr intmax_t operator""_jd(unsigned long long value) { return value; };
constexpr uintmax_t operator""_ju(unsigned long long value) { return value; };

constexpr int INF = 0x3f3f3f3f;
constexpr intmax_t LINF = 0x3f3f3f3f3f3f3f3f_jd;

template <class T, class Compare = less<>>
using MaxHeap = priority_queue<T, vector<T>, Compare>;
template <class T, class Compare = greater<>>
using MinHeap = priority_queue<T, vector<T>, Compare>;

inline void input() {}
template <class Head, class... Tail>
inline void input(Head &&head, Tail &&...tail) {
  cin >> head;
  input(forward<Tail>(tail)...);
}

template <class Container, class Value = typename Container::value_type,
          enable_if_t<!is_same<Container, string>::value, nullptr_t> = nullptr>
inline istream &operator>>(istream &is, Container &vs) {
  for (auto &v : vs)
    is >> v;
  return is;
}

inline void output() { cout << "\\n"; }
template <class Head, class... Tail>
inline void output(Head &&head, Tail &&...tail) {
  cout << head;
  if (sizeof...(tail))
    cout << " ";
  output(forward<Tail>(tail)...);
}

template <class Container, class Value = typename Container::value_type,
          enable_if_t<!is_same<Container, string>::value, nullptr_t> = nullptr>
inline ostream &operator<<(ostream &os, const Container &vs) {
  static constexpr const char *delim[] = {" ", ""};
  for (auto it = begin(vs); it != end(vs); ++it) {
    os << delim[it == begin(vs)] << *it;
  }
  return os;
}

template <class Iterator>
inline void join(const Iterator &Begin, const Iterator &End,
                 const string &delim = "\\n", const string &last = "\\n") {
  for (auto it = Begin; it != End; ++it) {
    cout << ((it == Begin) ? "" : delim) << *it;
  }
  cout << last;
}

template <class T> inline vector<T> makeVector(const T &initValue, size_t sz) {
  return vector<T>(sz, initValue);
}

template <class T, class... Args>
inline auto makeVector(const T &initValue, size_t sz, Args... args) {
  return vector<decltype(makeVector<T>(initValue, args...))>(
      sz, makeVector<T>(initValue, args...));
}

template <class Func> class FixPoint : Func {
public:
  explicit constexpr FixPoint(Func &&f) noexcept : Func(forward<Func>(f)) {}

  template <class... Args>
  constexpr decltype(auto) operator()(Args &&...args) const {
    return Func::operator()(*this, std::forward<Args>(args)...);
  }
};

template <class Func>
static inline constexpr decltype(auto) makeFixPoint(Func &&f) noexcept {
  return FixPoint<Func>{forward<Func>(f)};
}

template <class Container> struct reverse_t {
  Container &c;
  reverse_t(Container &c) : c(c) {}
  auto begin() { return c.rbegin(); }
  auto end() { return c.rend(); }
};

template <class Container> auto reversed(Container &c) {
  return reverse_t<Container>(c);
}

template <class T> inline bool chmax(T &a, const T &b) noexcept {
  return b > a && (a = b, true);
}

template <class T> inline bool chmin(T &a, const T &b) noexcept {
  return b < a && (a = b, true);
}

template <class T> inline T diff(const T &a, const T &b) noexcept {
  return a < b ? b - a : a - b;
}

void ioinit() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << fixed << setprecision(10);
  clog << fixed << setprecision(10);
}
// }}} End Header

// ModInt {{{
template <intmax_t Modulo> class ModInt {
public:
  using value_type = intmax_t;

private:
  static constexpr value_type cmod = Modulo; // compile-time
  static value_type rmod;                    // runtime
  value_type value = 0;

  static constexpr value_type inverse(value_type n, value_type m) {
    value_type a = n;
    value_type b = m;
    value_type x = 0;
    value_type y = 1;
    for (value_type u = y, v = x; a;) {
      const value_type t = b / a;
      swap(x -= t * u, u);
      swap(y -= t * v, v);
      swap(b -= t * a, a);
    }
    if ((x %= m) < 0)
      x += m;
    return x;
  }

  static value_type normalize(intmax_t n, value_type m) {
    if (n >= m) {
      n %= m;
    } else if (n < 0) {
      if ((n %= m) < 0)
        n += m;
    }
    return n;
  }

public:
  ModInt() = default;
  ModInt(intmax_t n) : value(normalize(n, getModulo())) {}

  template <typename T> constexpr explicit operator T() const {
    return static_cast<T>(value);
  }

  ModInt &operator=(intmax_t n) {
    value = normalize(n, getModulo());
    return *this;
  }

  ModInt &operator+=(const ModInt &other) {
    if ((value += other.value) >= getModulo())
      value -= getModulo();
    return *this;
  }
  ModInt &operator-=(const ModInt &other) {
    if ((value -= other.value) < 0)
      value += getModulo();
    return *this;
  }
  ModInt &operator*=(const ModInt &other) {
    value = (value * other.value) % getModulo();
    return *this;
  }
  ModInt &operator/=(const ModInt &other) {
    value = (value * inverse(other.value, getModulo())) % getModulo();
    return *this;
  }

  ModInt &operator++() {
    if (++value == getModulo())
      value = 0;
    return *this;
  }
  ModInt &operator--() {
    if (value-- == 0)
      value = getModulo() - 1;
    return *this;
  }

  ModInt operator++(int) {
    const ModInt tmp(*this);
    ++*this;
    return tmp;
  }
  ModInt operator--(int) {
    const ModInt tmp(*this);
    --*this;
    return tmp;
  }

  friend ModInt operator+(ModInt lhs, const ModInt &rhs) { return lhs += rhs; }
  friend ModInt operator-(ModInt lhs, const ModInt &rhs) { return lhs -= rhs; }
  friend ModInt operator*(ModInt lhs, const ModInt &rhs) { return lhs *= rhs; }
  friend ModInt operator/(ModInt lhs, const ModInt &rhs) { return lhs /= rhs; }

  ModInt operator+() const { return *this; }
  ModInt operator-() const {
    if (value == 0)
      return *this;
    return ModInt(getModulo() - value);
  }

  friend bool operator==(const ModInt &lhs, const ModInt &rhs) {
    return lhs.value == rhs.value;
  }
  friend bool operator!=(const ModInt &lhs, const ModInt &rhs) {
    return !(lhs == rhs);
  }

  friend ostream &operator<<(ostream &os, const ModInt &n) {
    return os << n.value;
  }
  friend istream &operator>>(istream &is, ModInt &n) {
    is >> n.value;
    n.value = normalize(n.value, getModulo());
    return is;
  }

  static value_type getModulo() { return ((cmod > 0) ? cmod : rmod); }

  template <int M = Modulo, typename T = typename enable_if<(M <= 0)>::type>
  static T setModulo(value_type m) {
    rmod = m;
  }
};

template <intmax_t M> constexpr typename ModInt<M>::value_type ModInt<M>::cmod;
template <intmax_t M> typename ModInt<M>::value_type ModInt<M>::rmod;
// }}}

// constexpr intmax_t MOD = intmax_t(1e9) + 7;
constexpr intmax_t MOD = 998244353;
using Mint = ModInt<MOD>;

// BinaryIndexedTree {{{
template <class T> struct BinaryIndexedTree {
  vector<T> bit;
  const size_t SIZE;

  explicit BinaryIndexedTree(size_t n)
      : bit(n + 5, 0), SIZE(1 << (__lg(n + 5) + 1)) {}

  void add(int i, const T &v) {
    for (++i; i < bit.size(); i += i & -i)
      bit[i] += v;
  }

  // [0, i]
  T sum(int i) const {
    T ret = 0;
    for (++i; i > 0; i -= i & -i)
      ret += bit[i];
    return ret;
  }

  // [s, t]
  T sum(int s, int t) const {
    if (s > t)
      swap(s, t);
    return sum(t) - sum(s - 1);
  }

  size_t lower_bound(T v) const {
    if (v <= 0)
      return 0;
    T x = 0;
    for (size_t k = SIZE; k > 0; k >>= 1) {
      if (x + k < bit.size() && bit[x + k] < v) {
        v -= bit[x + k];
        x += k;
      }
    }
    return x;
  }
};
// }}}

signed main() {
  ioinit();

  var(size_t, N, K);

  vector<intmax_t> L(K), R(K);
  rep(i, 0, K) input(L[i], R[i]);

  vector<Mint> dp(N + 1);
  // dp[i] := マス i に行く方法の総数
  vector<Mint> imos(N + 1);
  dp[1] = 1;
  repc(i, 1, N) {
    imos[i] += imos[i - 1];
    dp[i] += imos[i];
    rep(j, 0, K) {
      if (i + L[j] <= N)
        imos[i + L[j]] += dp[i];
      if (i + R[j] < N)
        imos[i + R[j] + 1] -= dp[i];
    }
  }

  output(dp[N]);
  return 0;
}


Error: TLE

Fixed submission:

#pragma GCC optimize("Ofast")
#include "bits/stdc++.h"

// Begin Header {{{
using namespace std;

#ifndef DEBUG
#define dump(...)
#endif

#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define rep(i, b, e) for (intmax_t i = (b), i##_limit = (e); i < i##_limit; ++i)
#define repc(i, b, e)                                                          \\
  for (intmax_t i = (b), i##_limit = (e); i <= i##_limit; ++i)
#define repr(i, b, e)                                                          \\
  for (intmax_t i = (b), i##_limit = (e); i >= i##_limit; --i)
#define var(Type, ...)                                                         \\
  Type __VA_ARGS__;                                                            \\
  input(__VA_ARGS__)

constexpr size_t operator""_zu(unsigned long long value) { return value; };
constexpr intmax_t operator""_jd(unsigned long long value) { return value; };
constexpr uintmax_t operator""_ju(unsigned long long value) { return value; };

constexpr int INF = 0x3f3f3f3f;
constexpr intmax_t LINF = 0x3f3f3f3f3f3f3f3f_jd;

template <class T, class Compare = less<>>
using MaxHeap = priority_queue<T, vector<T>, Compare>;
template <class T, class Compare = greater<>>
using MinHeap = priority_queue<T, vector<T>, Compare>;

inline void input() {}
template <class Head, class... Tail>
inline void input(Head &&head, Tail &&...tail) {
  cin >> head;
  input(forward<Tail>(tail)...);
}

template <class Container, class Value = typename Container::value_type,
          enable_if_t<!is_same<Container, string>::value, nullptr_t> = nullptr>
inline istream &operator>>(istream &is, Container &vs) {
  for (auto &v : vs)
    is >> v;
  return is;
}

inline void output() { cout << "\\n"; }
template <class Head, class... Tail>
inline void output(Head &&head, Tail &&...tail) {
  cout << head;
  if (sizeof...(tail))
    cout << " ";
  output(forward<Tail>(tail)...);
}

template <class Container, class Value = typename Container::value_type,
          enable_if_t<!is_same<Container, string>::value, nullptr_t> = nullptr>
inline ostream &operator<<(ostream &os, const Container &vs) {
  static constexpr const char *delim[] = {" ", ""};
  for (auto it = begin(vs); it != end(vs); ++it) {
    os << delim[it == begin(vs)] << *it;
  }
  return os;
}

template <class Iterator>
inline void join(const Iterator &Begin, const Iterator &End,
                 const string &delim = "\\n", const string &last = "\\n") {
  for (auto it = Begin; it != End; ++it) {
    cout << ((it == Begin) ? "" : delim) << *it;
  }
  cout << last;
}

template <class T> inline vector<T> makeVector(const T &initValue, size_t sz) {
  return vector<T>(sz, initValue);
}

template <class T, class... Args>
inline auto makeVector(const T &initValue, size_t sz, Args... args) {
  return vector<decltype(makeVector<T>(initValue, args...))>(
      sz, makeVector<T>(initValue, args...));
}

template <class Func> class FixPoint : Func {
public:
  explicit constexpr FixPoint(Func &&f) noexcept : Func(forward<Func>(f)) {}

  template <class... Args>
  constexpr decltype(auto) operator()(Args &&...args) const {
    return Func::operator()(*this, std::forward<Args>(args)...);
  }
};

template <class Func>
static inline constexpr decltype(auto) makeFixPoint(Func &&f) noexcept {
  return FixPoint<Func>{forward<Func>(f)};
}

template <class Container> struct reverse_t {
  Container &c;
  reverse_t(Container &c) : c(c) {}
  auto begin() { return c.rbegin(); }
  auto end() { return c.rend(); }
};

template <class Container> auto reversed(Container &c) {
  return reverse_t<Container>(c);
}

template <class T> inline bool chmax(T &a, const T &b) noexcept {
  return b > a && (a = b, true);
}

template <class T> inline bool chmin(T &a, const T &b) noexcept {
  return b < a && (a = b, true);
}

template <class T> inline T diff(const T &a, const T &b) noexcept {
  return a < b ? b - a : a - b;
}

void ioinit() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << fixed << setprecision(10);
  clog << fixed << setprecision(10);
}
// }}} End Header

// ModInt {{{
template <intmax_t Modulo> class ModInt {
public:
  using value_type = intmax_t;

private:
  static constexpr value_type cmod = Modulo; // compile-time
  static value_type rmod;                    // runtime
  value_type value = 0;

  static constexpr value_type inverse(value_type n, value_type m) {
    value_type a = n;
    value_type b = m;
    value_type x = 0;
    value_type y = 1;
    for (value_type u = y, v = x; a;) {
      const value_type t = b / a;
      swap(x -= t * u, u);
      swap(y -= t * v, v);
      swap(b -= t * a, a);
    }
    if ((x %= m) < 0)
      x += m;
    return x;
  }

  static value_type normalize(intmax_t n, value_type m) {
    if (n >= m) {
      n %= m;
    } else if (n < 0) {
      if ((n %= m) < 0)
        n += m;
    }
    return n;
  }

public:
  ModInt() = default;
  ModInt(intmax_t n) : value(normalize(n, getModulo())) {}

  template <typename T> constexpr explicit operator T() const {
    return static_cast<T>(value);
  }

  ModInt &operator=(intmax_t n) {
    value = normalize(n, getModulo());
    return *this;
  }

  ModInt &operator+=(const ModInt &other) {
    if ((value += other.value) >= getModulo())
      value -= getModulo();
    return *this;
  }
  ModInt &operator-=(const ModInt &other) {
    if ((value -= other.value) < 0)
      value += getModulo();
    return *this;
  }
  ModInt &operator*=(const ModInt &other) {
    value = (value * other.value) % getModulo();
    return *this;
  }
  ModInt &operator/=(const ModInt &other) {
    value = (value * inverse(other.value, getModulo())) % getModulo();
    return *this;
  }

  ModInt &operator++() {
    if (++value == getModulo())
      value = 0;
    return *this;
  }
  ModInt &operator--() {
    if (value-- == 0)
      value = getModulo() - 1;
    return *this;
  }

  ModInt operator++(int) {
    const ModInt tmp(*this);
    ++*this;
    return tmp;
  }
  ModInt operator--(int) {
    const ModInt tmp(*this);
    --*this;
    return tmp;
  }

  friend ModInt operator+(ModInt lhs, const ModInt &rhs) { return lhs += rhs; }
  friend ModInt operator-(ModInt lhs, const ModInt &rhs) { return lhs -= rhs; }
  friend ModInt operator*(ModInt lhs, const ModInt &rhs) { return lhs *= rhs; }
  friend ModInt operator/(ModInt lhs, const ModInt &rhs) { return lhs /= rhs; }

  ModInt operator+() const { return *this; }
  ModInt operator-() const {
    if (value == 0)
      return *this;
    return ModInt(getModulo() - value);
  }

  friend bool operator==(const ModInt &lhs, const ModInt &rhs) {
    return lhs.value == rhs.value;
  }
  friend bool operator!=(const ModInt &lhs, const ModInt &rhs) {
    return !(lhs == rhs);
  }

  friend ostream &operator<<(ostream &os, const ModInt &n) {
    return os << n.value;
  }
  friend istream &operator>>(istream &is, ModInt &n) {
    is >> n.value;
    n.value = normalize(n.value, getModulo());
    return is;
  }

  static value_type getModulo() { return ((cmod > 0) ? cmod : rmod); }

  template <int M = Modulo, typename T = typename enable_if<(M <= 0)>::type>
  static T setModulo(value_type m) {
    rmod = m;
  }
};

template <intmax_t M> constexpr typename ModInt<M>::value_type ModInt<M>::cmod;
template <intmax_t M> typename ModInt<M>::value_type ModInt<M>::rmod;
// }}}

// constexpr intmax_t MOD = intmax_t(1e9) + 7;
constexpr intmax_t MOD = 998244353;
using Mint = ModInt<MOD>;

signed main() {
  ioinit();

  var(size_t, N, K);

  vector<intmax_t> w;
  rep(i, 0, K) {
    var(intmax_t, L, R);
    repc(j, L, R) { w.emplace_back(j); }
  }

  sort(w.begin(), w.end(), greater<>());

  vector<Mint> dp(N + 1);
  dp[1] = 1;
  repc(j, 1, N) {
    for (const auto wi : w) {
      if (j + wi <= N) {
        dp[j + wi] += dp[j];
      }
    }
  }

  output(dp.back());
  return 0;
}