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

#include <bits/stdc++.h>
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define codefor                                                                \\
  int test;                                                                    \\
  scanf("%d", &test);                                                          \\
  while (test--)
#define INT(...)                                                               \\
  int __VA_ARGS__;                                                             \\
  in(__VA_ARGS__)
#define LL(...)                                                                \\
  ll __VA_ARGS__;                                                              \\
  in(__VA_ARGS__)
#define yn(ans)                                                                \\
  if (ans)                                                                     \\
    printf("Yes\\n");                                                           \\
  else                                                                         \\
    printf("No\\n")
#define YN(ans)                                                                \\
  if (ans)                                                                     \\
    printf("YES\\n");                                                           \\
  else                                                                         \\
    printf("NO\\n")
#define vector1d(type, name, ...) vector<type> name(__VA_ARGS__)
#define vector2d(type, name, h, ...)                                           \\
  vector<vector<type>> name(h, vector<type>(__VA_ARGS__))
#define umap unordered_map
#define uset unordered_set
using namespace std;
using ll = long long;
const int MOD = 998244353;
// 入力系
void scan(int &a) { scanf("%d", &a); }
void scan(long long &a) { scanf("%lld", &a); }
template <class T> void scan(T &a) { cin >> a; }
template <class T> void scan(vector<T> &vec) {
  for (auto &&it : vec)
    scan(it);
}
void in() {}
template <class Head, class... Tail> void in(Head &head, Tail &...tail) {
  scan(head);
  in(tail...);
}
// 出力系
void print(const int &a) { printf("%d", a); }
void print(const long long &a) { printf("%lld", a); }
void print(const double &a) { printf("%.15lf", a); }
template <class T> void print(const T &a) { cout << a; }
template <class T> void print(const vector<T> &vec) {
  if (vec.empty())
    return;
  print(vec[0]);
  for (auto it = vec.begin(); ++it != vec.end();) {
    putchar(' ');
    print(*it);
  }
}
void out() { putchar('\\n'); }
template <class T> void out(const T &t) {
  print(t);
  putchar('\\n');
}
template <class Head, class... Tail>
void out(const Head &head, const Tail &...tail) {
  print(head);
  putchar(' ');
  out(tail...);
}
// デバッグ系
template <class T> void dprint(const T &a) { cerr << a; }
template <class T> void dprint(const vector<T> &vec) {
  if (vec.empty())
    return;
  cerr << vec[0];
  for (auto it = vec.begin(); ++it != vec.end();) {
    cerr << " " << *it;
  }
}
void debug() { cerr << endl; }
template <class T> void debug(const T &t) {
  dprint(t);
  cerr << endl;
}
template <class Head, class... Tail>
void debug(const Head &head, const Tail &...tail) {
  dprint(head);
  cerr << " ";
  debug(tail...);
}
ll intpow(ll a, ll b) {
  ll ans = 1;
  while (b) {
    if (b & 1)
      ans *= a;
    a *= a;
    b /= 2;
  }
  return ans;
}
ll modpow(ll a, ll b, ll p) {
  ll ans = 1;
  while (b) {
    if (b & 1)
      (ans *= a) %= p;
    (a *= a) %= p;
    b /= 2;
  }
  return ans;
}
ll updivide(ll a, ll b) {
  if (b == 1)
    return a;
  else if (a % b == 0)
    return a / b;
  else
    return (a / b) + 1;
}

int main() {
  INT(n, k);
  vector<pair<int, int>> step(k);
  int l, r;
  rep(i, k) {
    in(l, r);
    step[i] = make_pair(l, r);
  }
  sort(all(step));
  vector<ll> dp(n + 1, 0), dpsum(n + 1, 0);
  dp[1] = 1;
  dpsum[1] = 1;
  int left, right;
  for (int i = 2; i <= n; i++) {
    for (int j = 0; j < k; j++) {
      left = max(i - step[j].second - 1, 0);
      right = max(i - step[j].first, 0);
      dp[i] += dpsum[right] - dpsum[left];
      if (dp[i] < 0)
        dp[i] += MOD;
      else
        dp[i] %= MOD;
    }
    dpsum[i] = dpsum[i - 1] + dp[i];
    dpsum[i] %= MOD;
  }
  out(dp[n]);
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define codefor                                                                \\
  int test;                                                                    \\
  scanf("%d", &test);                                                          \\
  while (test--)
#define INT(...)                                                               \\
  int __VA_ARGS__;                                                             \\
  in(__VA_ARGS__)
#define LL(...)                                                                \\
  ll __VA_ARGS__;                                                              \\
  in(__VA_ARGS__)
#define yn(ans)                                                                \\
  if (ans)                                                                     \\
    printf("Yes\\n");                                                           \\
  else                                                                         \\
    printf("No\\n")
#define YN(ans)                                                                \\
  if (ans)                                                                     \\
    printf("YES\\n");                                                           \\
  else                                                                         \\
    printf("NO\\n")
#define vector1d(type, name, ...) vector<type> name(__VA_ARGS__)
#define vector2d(type, name, h, ...)                                           \\
  vector<vector<type>> name(h, vector<type>(__VA_ARGS__))
#define umap unordered_map
#define uset unordered_set
using namespace std;
using ll = long long;
const int MOD = 998244353;
// 入力系
void scan(int &a) { scanf("%d", &a); }
void scan(long long &a) { scanf("%lld", &a); }
template <class T> void scan(T &a) { cin >> a; }
template <class T> void scan(vector<T> &vec) {
  for (auto &&it : vec)
    scan(it);
}
void in() {}
template <class Head, class... Tail> void in(Head &head, Tail &...tail) {
  scan(head);
  in(tail...);
}
// 出力系
void print(const int &a) { printf("%d", a); }
void print(const long long &a) { printf("%lld", a); }
void print(const double &a) { printf("%.15lf", a); }
template <class T> void print(const T &a) { cout << a; }
template <class T> void print(const vector<T> &vec) {
  if (vec.empty())
    return;
  print(vec[0]);
  for (auto it = vec.begin(); ++it != vec.end();) {
    putchar(' ');
    print(*it);
  }
}
void out() { putchar('\\n'); }
template <class T> void out(const T &t) {
  print(t);
  putchar('\\n');
}
template <class Head, class... Tail>
void out(const Head &head, const Tail &...tail) {
  print(head);
  putchar(' ');
  out(tail...);
}
// デバッグ系
template <class T> void dprint(const T &a) { cerr << a; }
template <class T> void dprint(const vector<T> &vec) {
  if (vec.empty())
    return;
  cerr << vec[0];
  for (auto it = vec.begin(); ++it != vec.end();) {
    cerr << " " << *it;
  }
}
void debug() { cerr << endl; }
template <class T> void debug(const T &t) {
  dprint(t);
  cerr << endl;
}
template <class Head, class... Tail>
void debug(const Head &head, const Tail &...tail) {
  dprint(head);
  cerr << " ";
  debug(tail...);
}
ll intpow(ll a, ll b) {
  ll ans = 1;
  while (b) {
    if (b & 1)
      ans *= a;
    a *= a;
    b /= 2;
  }
  return ans;
}
ll modpow(ll a, ll b, ll p) {
  ll ans = 1;
  while (b) {
    if (b & 1)
      (ans *= a) %= p;
    (a *= a) %= p;
    b /= 2;
  }
  return ans;
}
ll updivide(ll a, ll b) {
  if (b == 1)
    return a;
  else if (a % b == 0)
    return a / b;
  else
    return (a / b) + 1;
}

int main() {
  INT(n, k);
  vector<int> step;
  int l, r;
  rep(i, k) {
    in(l, r);
    for (int j = l; j <= r; j++) {
      step.push_back(j);
    }
  }
  // debug(step);
  sort(all(step));
  vector<ll> dp(n + 1, 0);
  dp[1] = 1;
  for (int i = 1; i <= n; i++) {
    if (dp[i] == 0)
      continue;
    for (int j = 0; j < step.size(); j++) {
      if (i + step[j] <= n) {
        dp[i + step[j]] += dp[i];
        dp[i + step[j]] %= MOD;
      } else {
        step.erase(step.begin() + j);
        j--;
      }
    }
  }
  out(dp[n]);
}