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

#include <algorithm>
#include <bit>
#include <bitset>
#include <cctype>
#include <cmath>
#include <cstdint>
#include <cstring>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <time.h>
#include <tuple>
#include <vector>
using namespace std;
const double PI = 3.14159265358979323846;
const long long int MOD = 1000000000 + 7;
using ll = long long;

struct UnionFind {
  vector<int> parent;

  UnionFind(int N) : parent(N) {
    for (int i = 0; i < N; i++) {
      parent[i] = -1;
    }
  }

  int root(int i) {
    if (parent[i] < 0) {
      return i;
    }
    return (parent[i] = root(parent[i]));
  }

  bool unite(int from, int to) {
    int rx = root(from);
    int ry = root(to);
    if (rx != ry) {
      parent[ry] += parent[rx];
      parent[rx] = ry;

      return true;
    } else {
      return false;
    }
  }

  bool same(int x, int y) { return root(x) == root(y); }

  int treeSize(int x) { return -parent[root(x)]; }
};

long long int modpow(long long int base, long long int pow, long long int mod) {
  if (pow == 1) {
    return base;
  } else if (pow == 0) {
    return 1;
  }

  if (pow % 2 == 0) {
    auto temp = modpow(base, pow / 2, mod);
    return (temp * temp) % mod;
  } else {
    return (base * modpow(base, pow - 1, mod)) % mod;
  }
}

long long int moddiv(long long int X, long long int Y, long long int mod) {
  auto fermatDiv = modpow(Y, mod - 2, mod);

  return (X * fermatDiv) % mod;
}

long long modCombination(long long left, long long right, long long int mod) {
  long long answer = 1;
  if (left > right) {
    for (long long i = 0; i < right; i++) {
      answer = (answer * (left - i)) % mod;
      answer = moddiv(answer, (i + 1), mod);
    }
  }
  return answer;
}

bool IsPrime(long long N) {
  if (N == 1) {
    return false;
  }
  for (long long i = 2; i * i <= N; i++) {
    if (N % i == 0) {
      return false;
    }
  }

  return true;
}

vector<pair<long long, long long>> prime_factorize(long long N) {
  vector<pair<long long, long long>> res;
  for (long long a = 2; a * a <= N; ++a) {
    if (N % a != 0)
      continue;
    long long ex = 0; // 指数

    // 割れる限り割り続ける
    while (N % a == 0) {
      ++ex;
      N /= a;
    }

    // その結果を push
    res.push_back({a, ex});
  }

  // 最後に残った数について
  if (N != 1)
    res.push_back({N, 1});
  return res;
}

vector<long long> enum_divisors(long long N) {
  vector<long long> res;
  for (long long i = 1; i * i <= N; ++i) {
    if (N % i == 0) {
      res.push_back(i);
      // 重複しないならば i の相方である N/i も push
      if (N / i != i)
        res.push_back(N / i);
    }
  }
  // 小さい順に並び替える
  sort(res.begin(), res.end());
  return res;
}

long long gcd(long long a, long long b) {
  if (b > a) {
    long long temp = b;
    b = a;
    a = temp;
  }
  // cout << "a:" << a << "b:" << b << endl;
  long long c = a % b;
  if (c == 0) {
    return b;
  } else {
    return gcd(b, c);
  }
}

int main() {

  ll mod = 998244353;

  ll N, K;
  cin >> N >> K;

  /*vector<ll> numbers;

  for (ll i = 0; i < K; i++) {
      ll L, R;
      cin >> L >> R;
      for (ll j = L; j <= R; j++) {
          numbers.push_back(j);
      }
  }*/

  vector<ll> Ls(K), Rs(K);

  for (ll i = 0; i < K; i++) {
    ll L, R;
    cin >> L >> R;
    Ls[i] = L;
    Rs[i] = R;
  }

  vector<ll> patterns(N, 0);
  patterns[0] = 1;

  vector<ll> headIndices(K), tailIndices(K), rangeTotals(K);

  for (ll i = 0; i < K; i++) {
    headIndices[i] = -Rs[i];
    tailIndices[i] = -Ls[i];
    rangeTotals[i] = 0;
  }

  for (ll i = 1; i < N; i++) {
    for (ll j = 0; j < K; j++) {
      if (headIndices[j] >= 0) {
        rangeTotals[j] -= patterns[headIndices[j]];
        rangeTotals[j] += mod;
        rangeTotals[j] %= mod;
      }
      headIndices[j]++;
      tailIndices[j]++;
      if (tailIndices[j] >= 0) {
        rangeTotals[j] += patterns[tailIndices[j]];
      }
      rangeTotals[j] %= mod;
      patterns[i] += rangeTotals[j];
      patterns[i] %= mod;
    }
  }

  /*for (ll i = 1; i < N; i++) {
      for (auto n : numbers) {
          if (i - n >= 0) {
              patterns[i] += patterns[i - n];
              patterns[i] %= mod;
          }
      }
  }*/

  cout << patterns[N - 1] << endl;
  return 0;
}


Error: TLE

Fixed submission:

#include <algorithm>
#include <bit>
#include <bitset>
#include <cctype>
#include <cmath>
#include <cstdint>
#include <cstring>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <time.h>
#include <tuple>
#include <vector>
using namespace std;
const double PI = 3.14159265358979323846;
const long long int MOD = 1000000000 + 7;
using ll = long long;

struct UnionFind {
  vector<int> parent;

  UnionFind(int N) : parent(N) {
    for (int i = 0; i < N; i++) {
      parent[i] = -1;
    }
  }

  int root(int i) {
    if (parent[i] < 0) {
      return i;
    }
    return (parent[i] = root(parent[i]));
  }

  bool unite(int from, int to) {
    int rx = root(from);
    int ry = root(to);
    if (rx != ry) {
      parent[ry] += parent[rx];
      parent[rx] = ry;

      return true;
    } else {
      return false;
    }
  }

  bool same(int x, int y) { return root(x) == root(y); }

  int treeSize(int x) { return -parent[root(x)]; }
};

long long int modpow(long long int base, long long int pow, long long int mod) {
  if (pow == 1) {
    return base;
  } else if (pow == 0) {
    return 1;
  }

  if (pow % 2 == 0) {
    auto temp = modpow(base, pow / 2, mod);
    return (temp * temp) % mod;
  } else {
    return (base * modpow(base, pow - 1, mod)) % mod;
  }
}

long long int moddiv(long long int X, long long int Y, long long int mod) {
  auto fermatDiv = modpow(Y, mod - 2, mod);

  return (X * fermatDiv) % mod;
}

long long modCombination(long long left, long long right, long long int mod) {
  long long answer = 1;
  if (left > right) {
    for (long long i = 0; i < right; i++) {
      answer = (answer * (left - i)) % mod;
      answer = moddiv(answer, (i + 1), mod);
    }
  }
  return answer;
}

bool IsPrime(long long N) {
  if (N == 1) {
    return false;
  }
  for (long long i = 2; i * i <= N; i++) {
    if (N % i == 0) {
      return false;
    }
  }

  return true;
}

vector<pair<long long, long long>> prime_factorize(long long N) {
  vector<pair<long long, long long>> res;
  for (long long a = 2; a * a <= N; ++a) {
    if (N % a != 0)
      continue;
    long long ex = 0; // 指数

    // 割れる限り割り続ける
    while (N % a == 0) {
      ++ex;
      N /= a;
    }

    // その結果を push
    res.push_back({a, ex});
  }

  // 最後に残った数について
  if (N != 1)
    res.push_back({N, 1});
  return res;
}

vector<long long> enum_divisors(long long N) {
  vector<long long> res;
  for (long long i = 1; i * i <= N; ++i) {
    if (N % i == 0) {
      res.push_back(i);
      // 重複しないならば i の相方である N/i も push
      if (N / i != i)
        res.push_back(N / i);
    }
  }
  // 小さい順に並び替える
  sort(res.begin(), res.end());
  return res;
}

long long gcd(long long a, long long b) {
  if (b > a) {
    long long temp = b;
    b = a;
    a = temp;
  }
  // cout << "a:" << a << "b:" << b << endl;
  long long c = a % b;
  if (c == 0) {
    return b;
  } else {
    return gcd(b, c);
  }
}

int main() {

  ll mod = 998244353;

  ll N, K;
  cin >> N >> K;

  vector<ll> numbers;

  for (ll i = 0; i < K; i++) {
    ll L, R;
    cin >> L >> R;
    for (ll j = L; j <= R; j++) {
      numbers.push_back(j);
    }
  }

  vector<ll> patterns(N, 0);
  patterns[0] = 1;

  for (ll i = 1; i < N; i++) {
    for (auto n : numbers) {
      if (i - n >= 0) {
        patterns[i] += patterns[i - n];
        patterns[i] %= mod;
      }
    }
  }

  cout << patterns[N - 1] << endl;
  return 0;
}