Problem p02549 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int, int>;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, a, b) for (int i = a; i < b; i++)
#define each(i, mp) for (auto &i : mp)

const int INF = 1001001001;
const int takahashi = 998244353;
const int mod = 998244353;
struct mint {
  ll x; // typedef long long ll;
  mint(ll x = 0) : x((x % mod + mod) % mod) {}

  mint operator-() const { return mint(-x); }

  mint &operator+=(const mint a) {
    if ((x += a.x) >= mod) {
      x -= mod;
    }

    return *this;
  }

  mint &operator-=(const mint a) {
    if ((x += mod - a.x) >= mod) {
      x -= mod;
    }

    return *this;
  }

  mint &operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }

  mint operator+(const mint a) const { return mint(*this) += a; }

  mint operator-(const mint a) const { return mint(*this) -= a; }

  mint operator*(const mint a) const { return mint(*this) *= a; }

  mint pow(ll t) const {
    if (!t) {
      return 1;
    }
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1) {
      a *= *this;
    }

    return a;
  }

  // for prime mod
  mint inv() const { return pow(mod - 2); }

  mint &operator/=(const mint a) { return *this *= a.inv(); }

  mint operator/(const mint a) const { return mint(*this) /= a; }
};

istream &operator>>(istream &is, mint &a) { return is >> a.x; }

ostream &operator<<(ostream &os, const mint &a) { return os << a.x; }

ll ans = 0;
int n, k;
ll minus_counter(ll n, ll tmp) {
  ll counter = 0;
  while (1) {
    n -= tmp;
    if (n < 0) {
      return counter;
    } else {
      counter++;
    }
  }
}

int main() {
  cin >> n >> k;
  vector<int> l(k);
  vector<int> r(k);
  rep(i, k) {
    cin >> l[i];
    cin >> r[i];
  }
  // vector <int> s;
  // rep(i, k) {
  //   repr(j, l[i], r[i] + 1) {
  //     s.push_back(j);
  //   }
  //   if (l[i] == r[i]) { s.push_back(l[i]); }
  // }
  // sort(s.begin(), s.end());
  // s.erase(std::unique(s.begin(), s.end()), s.end());
  // vector <ll> save_counter;
  // rep(i, s.size()) {
  //   save_counter.push_back(minus_counter(n, s[i]));
  // }
  vector<mint> dp(n + 1);
  vector<mint> dpsum(n + 1);
  dp[1] = 1;
  dpsum[1] = 1;
  for (int i = 2; i <= n; ++i) {
    rep(j, k) {
      // [l[i], r[i]]
      int li = i - r[j];
      int ri = i - l[j];
      if (ri < 0) {
        continue;
      }
      li = max(li, 1);
      dp[i] += dpsum[ri] - dpsum[li - 1]; // dp[li]~dp[ri];
    }
    dpsum[i] = dpsum[i - 1] + dp[i];
  }
  cout << dp[n] << endl;

  return 0;
}


Error: 0

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int, int>;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, a, b) for (int i = a; i < b; i++)
#define each(i, mp) for (auto &i : mp)

const int INF = 1001001001;
const int takahashi = 998244353;
const int mod = 998244353;
struct mint {
  ll x; // typedef long long ll;
  mint(ll x = 0) : x((x % mod + mod) % mod) {}

  mint operator-() const { return mint(-x); }

  mint &operator+=(const mint a) {
    if ((x += a.x) >= mod) {
      x -= mod;
    }

    return *this;
  }

  mint &operator-=(const mint a) {
    if ((x += mod - a.x) >= mod) {
      x -= mod;
    }

    return *this;
  }

  mint &operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }

  mint operator+(const mint a) const { return mint(*this) += a; }

  mint operator-(const mint a) const { return mint(*this) -= a; }

  mint operator*(const mint a) const { return mint(*this) *= a; }

  mint pow(ll t) const {
    if (!t) {
      return 1;
    }
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1) {
      a *= *this;
    }

    return a;
  }

  // for prime mod
  mint inv() const { return pow(mod - 2); }

  mint &operator/=(const mint a) { return *this *= a.inv(); }

  mint operator/(const mint a) const { return mint(*this) /= a; }
};

istream &operator>>(istream &is, mint &a) { return is >> a.x; }

ostream &operator<<(ostream &os, const mint &a) { return os << a.x; }

ll ans = 0;
int n, k;
ll minus_counter(ll n, ll tmp) {
  ll counter = 0;
  while (1) {
    n -= tmp;
    if (n < 0) {
      return counter;
    } else {
      counter++;
    }
  }
}

int main() {
  cin >> n >> k;
  vector<int> l(k);
  vector<int> r(k);
  rep(i, k) {
    cin >> l[i];
    cin >> r[i];
  }
  vector<int> s;
  rep(i, k) {
    repr(j, l[i], r[i] + 1) { s.push_back(j); }
    if (l[i] == r[i]) {
      s.push_back(l[i]);
    }
  }
  sort(s.begin(), s.end());
  s.erase(std::unique(s.begin(), s.end()), s.end());
  // vector <ll> save_counter;
  // rep(i, s.size()) {
  //   save_counter.push_back(minus_counter(n, s[i]));
  // }
  vector<mint> dp(n + 1);
  dp[1] = 1;
  repr(i, 1, n) {
    // dp[i] %= takahashi;
    rep(j, s.size()) {
      if (i + j < n) {
        dp[i + s[j]] += dp[i];
      }
      // std::cout << "s = " << s[i] << '\\n';
    }
    // std::cout << "dp" << dp[i] << '\\n';
  }

  cout << dp[n] << endl;

  return 0;
}