Problem p02549 (C++)

Buggy submission (status: Time Limit Exceeded):
/*
これを入れて実行
g++ code.cpp
./a.out
 */

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <stdio.h>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#define all(x) (x).begin(), (x).end()
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

using namespace std;
typedef long long ll;
typedef long double ld;

int dy4[4] = {-1, 0, +1, 0};
int dx4[4] = {0, +1, 0, -1};
int dy8[8] = {-1, -1, 0, 1, 1, 1, 0, -1};
int dx8[8] = {0, 1, 1, 1, 0, -1, -1, -1};

const long long INF = 1LL << 60;
const ll MOD = 1e9 + 7;

bool greaterSecond(const pair<int, int> &f, const pair<int, int> &s) {
  return f.second > s.second;
}

ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}

ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }

ll conbinationMemo[100][100];

void cmemoInit() {
  rep(i, 100) {
    rep(j, 100) { conbinationMemo[i][j] = -1; }
  }
}

ll nCr(ll n, ll r) {
  if (conbinationMemo[n][r] != -1)
    return conbinationMemo[n][r];
  if (r == 0 || r == n) {
    return 1;
  } else if (r == 1) {
    return n;
  }
  return conbinationMemo[n][r] = (nCr(n - 1, r) + nCr(n - 1, r - 1));
}

ll nPr(ll n, ll r) {
  r = n - r;
  ll ret = 1;
  for (ll i = n; i >= r + 1; i--)
    ret *= i;
  return ret;
}
//-----------------------ここから-----------
ll mod = 998244353;
int main(void) {
  ll n, k;
  cin >> n >> k;
  vector<pair<ll, ll>> vec;
  rep(i, k) {
    ll l, r;
    cin >> l >> r;
    vec.push_back({l, r});
  }
  sort(all(vec));
  ll dp[200100];
  dp[0] = 1;
  dp[1] = -1;
  ll now = 0;
  rep(i, n) {
    now += dp[i];
    while (now < 0)
      now += mod;
    now %= mod;
    rep(j, vec.size()) {
      if (i + vec[j].first < n) {
        dp[i + vec[j].first] += now;
        dp[i + vec[j].first] %= mod;
      }
      if (i + vec[j].second + 1 < n) {
        dp[i + vec[j].second + 1] -= now;
        while (dp[i + vec[j].second + 1] < 0)
          dp[i + vec[j].second + 1] += mod;
        dp[i + vec[j].second + 1] %= mod;
      }
    }
  }
  while (now < 0)
    now += mod;
  cout << now % mod << endl;
}


Fixed submission:
/*
これを入れて実行
g++ code.cpp
./a.out
 */

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <stdio.h>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#define all(x) (x).begin(), (x).end()
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

using namespace std;
typedef long long ll;
typedef long double ld;

int dy4[4] = {-1, 0, +1, 0};
int dx4[4] = {0, +1, 0, -1};
int dy8[8] = {-1, -1, 0, 1, 1, 1, 0, -1};
int dx8[8] = {0, 1, 1, 1, 0, -1, -1, -1};

const long long INF = 1LL << 60;
const ll MOD = 1e9 + 7;

bool greaterSecond(const pair<int, int> &f, const pair<int, int> &s) {
  return f.second > s.second;
}

ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}

ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }

ll conbinationMemo[100][100];

void cmemoInit() {
  rep(i, 100) {
    rep(j, 100) { conbinationMemo[i][j] = -1; }
  }
}

ll nCr(ll n, ll r) {
  if (conbinationMemo[n][r] != -1)
    return conbinationMemo[n][r];
  if (r == 0 || r == n) {
    return 1;
  } else if (r == 1) {
    return n;
  }
  return conbinationMemo[n][r] = (nCr(n - 1, r) + nCr(n - 1, r - 1));
}

ll nPr(ll n, ll r) {
  r = n - r;
  ll ret = 1;
  for (ll i = n; i >= r + 1; i--)
    ret *= i;
  return ret;
}
//-----------------------ここから-----------
ll mod = 998244353;
int main(void) {
  ll n, k;
  cin >> n >> k;
  vector<pair<ll, ll>> vec;
  rep(i, k) {
    ll l, r;
    cin >> l >> r;
    vec.push_back({l, r});
  }
  sort(all(vec));
  ll dp[200100] = {0};
  dp[0] = 1;
  dp[1] = -1;
  ll now = 0;
  rep(i, n) {
    now += dp[i];
    while (now < 0)
      now += mod;
    now %= mod;
    rep(j, vec.size()) {
      if (i + vec[j].first < n) {
        dp[i + vec[j].first] += now;
        dp[i + vec[j].first] %= mod;
      }
      if (i + vec[j].second + 1 < n) {
        dp[i + vec[j].second + 1] -= now;
        while (dp[i + vec[j].second + 1] < 0)
          dp[i + vec[j].second + 1] += mod;
        dp[i + vec[j].second + 1] %= mod;
      }
    }
  }
  while (now < 0)
    now += mod;
  cout << now % mod << endl;
}