Problem p02702 (C++) — buggy submission, verdict: Time Limit Exceeded

#include "bits/stdc++.h"
#include <unordered_set>
#define rep(i, n) for (int i = 0; i < n; i++)
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
#define vll vector<vector<long long>>
#define vl vector<long long>
#define vi vector<int>
#define vii vector<vector<int>>
#define pb push_back
#define pf push_front
#define ld long double
#define Sort(a) sort(a.begin(), a.end())
#define cSort(a, cmp) sort(a.begin(), a.end(), cmp)
#define reSort(a) sort(a.rbegin(), a.rend())
static const ll llMAX = numeric_limits<long long>::max();
static const int intMAX = numeric_limits<int>::max();
static const ll llMIN = numeric_limits<long long>::min();
static const int intMIN = numeric_limits<int>::min();
static const ll d_5 = 100000;
static const ll d9_7 = 1000000007;
static const ll d_9 = 1000000000;
static const double PI = 3.14159265358979323846;
template <class T> T gcd(T a, T b) {
  if (a == 0) {
    return b;

  } else if (b == 0) {
    return a;
  }
  while (1) {
    if (a < b)
      swap(a, b);
    if (!b)
      break;
    a %= b;
  }
  return a;
}
ll digitpower(ll a, ll b) { // aのb乗を計算
  if (b == 1) {
    return a;
  } else if (b == 0) {
    return 1;
  }
  int mode = 0;
  if (mode == 0) {
    if (b % 2 == 1) {
      ll tmp = digitpower(a, (b - 1) / 2);
      tmp %= d9_7;
      tmp *= tmp;
      tmp %= d9_7;
      tmp *= a;
      return (tmp) % d9_7;
    } else {
      ll tmp = digitpower(a, (b) / 2);
      tmp %= d9_7;
      tmp *= tmp;
      tmp %= d9_7;
      return (tmp) % d9_7;
    }
  } else {
    if (b % 2 == 1) {
      ll tmp = digitpower(a, (b - 1) / 2);
      tmp *= tmp;
      tmp *= a;
      return (tmp);
    } else {
      ll tmp = digitpower(a, (b) / 2);
      tmp *= tmp;
      return (tmp);
    }
  }
  return 0;
}
template <class T> void Printvector(std::vector<T> &a) {
  int size = a.size();
  rep(i, size) { cout << a[i] << " "; }
  cout << endl;
}
template <class T> void Printvector(std::vector<std::vector<T>> &a) {
  int size = a.size();
  rep(i, size) {
    int size2 = a[i].size();
    rep(j, size2) { cout << a[i][j] << " "; }
    cout << endl;
  }
  cout << endl;
}
unordered_set<ll> primes(ll n) {
  unordered_set<ll> ret;
  for (ll i = 2; i * i <= n; i++) {
    if (n % i == 0) {
      ret.insert(i);
      ret.insert(n / i);
    }
  }
  return ret;
}
long long modinv(long long a, long long m) { // modの逆元
  long long b = m, u = 1, v = 0;
  while (b) {
    long long t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  u %= m;
  if (u < 0)
    u += m;
  return u;
}
struct c {
  ll a;
  ll b;
};

// 比較関数を定義
bool cmp(const c &left, const c &right) { return left.b > right.b; }
int main(void) {
  string s;
  cin >> s;
  int n = s.size();
  vi dp(2019, 0);
  int ans = 0;
  for (int i = 0; i < n; i++) {
    vi dp2(2019, 0);
    for (int j = 0; j < 2019; j++) {
      dp2[(j * 10 + s[i] - '0') % 2019] += dp[j];
    }
    dp2[s[i] - '0'] += 1;
    ans += dp2[0];
    dp = dp2;
  }
  // Printvector(dp);
  cout << ans << endl;
  return 0;
}

// clang++ -g -fsanitize=address -fno-omit-frame-pointer 1.cpp -o test.exe

//<<std::setprecision(30)

// 重複削除
/* std::sort(vec.begin(), vec.end());

 vec.erase(std::unique(vec.begin(), vec.end()), vec.end());*/

// ペアの全探索
/*do{
              int s=0;
              for(int i=0;i<n/2;i++)s+=v[i]^v[i+n/2];
              r=max(s,r);
              reverse(v.begin()+n/2,v.end());
      }while(next_permutation(v.begin(),v.end()));*/


Error: TLE

Fixed submission:

#include "bits/stdc++.h"
#include <unordered_set>
#define rep(i, n) for (int i = 0; i < n; i++)
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
#define vll vector<vector<long long>>
#define vl vector<long long>
#define vi vector<int>
#define vii vector<vector<int>>
#define pb push_back
#define pf push_front
#define ld long double
#define Sort(a) sort(a.begin(), a.end())
#define cSort(a, cmp) sort(a.begin(), a.end(), cmp)
#define reSort(a) sort(a.rbegin(), a.rend())
static const ll llMAX = numeric_limits<long long>::max();
static const int intMAX = numeric_limits<int>::max();
static const ll llMIN = numeric_limits<long long>::min();
static const int intMIN = numeric_limits<int>::min();
static const ll d_5 = 100000;
static const ll d9_7 = 1000000007;
static const ll d_9 = 1000000000;
static const double PI = 3.14159265358979323846;
template <class T> T gcd(T a, T b) {
  if (a == 0) {
    return b;

  } else if (b == 0) {
    return a;
  }
  while (1) {
    if (a < b)
      swap(a, b);
    if (!b)
      break;
    a %= b;
  }
  return a;
}
ll digitpower(ll a, ll b) { // aのb乗を計算
  if (b == 1) {
    return a;
  } else if (b == 0) {
    return 1;
  }
  int mode = 0;
  if (mode == 0) {
    if (b % 2 == 1) {
      ll tmp = digitpower(a, (b - 1) / 2);
      tmp %= d9_7;
      tmp *= tmp;
      tmp %= d9_7;
      tmp *= a;
      return (tmp) % d9_7;
    } else {
      ll tmp = digitpower(a, (b) / 2);
      tmp %= d9_7;
      tmp *= tmp;
      tmp %= d9_7;
      return (tmp) % d9_7;
    }
  } else {
    if (b % 2 == 1) {
      ll tmp = digitpower(a, (b - 1) / 2);
      tmp *= tmp;
      tmp *= a;
      return (tmp);
    } else {
      ll tmp = digitpower(a, (b) / 2);
      tmp *= tmp;
      return (tmp);
    }
  }
  return 0;
}
template <class T> void Printvector(std::vector<T> &a) {
  int size = a.size();
  rep(i, size) { cout << a[i] << " "; }
  cout << endl;
}
template <class T> void Printvector(std::vector<std::vector<T>> &a) {
  int size = a.size();
  rep(i, size) {
    int size2 = a[i].size();
    rep(j, size2) { cout << a[i][j] << " "; }
    cout << endl;
  }
  cout << endl;
}
unordered_set<ll> primes(ll n) {
  unordered_set<ll> ret;
  for (ll i = 2; i * i <= n; i++) {
    if (n % i == 0) {
      ret.insert(i);
      ret.insert(n / i);
    }
  }
  return ret;
}
long long modinv(long long a, long long m) { // modの逆元
  long long b = m, u = 1, v = 0;
  while (b) {
    long long t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  u %= m;
  if (u < 0)
    u += m;
  return u;
}
vl facs(1000008, -1);
ll Factrial(ll num) {
  if (facs[num] != -1) {
    return facs[num];
  }
  if (num == 1 || num <= 0) {
    return 1;
  } else if (num < 0) {
    printf("ERROR_minus\\n");
    return 0;
  } else {
    facs[num] = (num * Factrial(num - 1)) % d9_7;
    return facs[num];
  }
}
struct c {
  ll a;
  ll b;
};

// 比較関数を定義
bool cmp(const c &left, const c &right) { return left.b > right.b; }
int main(void) {
  string s;
  cin >> s;
  int n = s.size();
  vll dp(2019, vl(n + 1, 0));
  ll ans = 0;
  unordered_set<int> d;
  d.insert(0);
  for (int i = 0; i < n; i++) {
    unordered_set<int> next;
    for (auto j : d) {
      dp[(j * 10 + s[i] - '0') % 2019][i + 1] += dp[j][i];
      next.insert((j * 10 + s[i] - '0') % 2019);
    }
    dp[s[i] - '0'][i + 1] += 1;
    next.insert(s[i] - '0');
    ans += dp[0][i + 1];
    d = next;
  }
  // Printvector(dp);
  cout << ans << endl;
  return 0;
}

// clang++ -g -fsanitize=address -fno-omit-frame-pointer 1.cpp -o test.exe

//<<std::setprecision(30)

// 重複削除
/* std::sort(vec.begin(), vec.end());

 vec.erase(std::unique(vec.begin(), vec.end()), vec.end());*/

// ペアの全探索
/*do{
              int s=0;
              for(int i=0;i<n/2;i++)s+=v[i]^v[i+n/2];
              r=max(s,r);
              reverse(v.begin()+n/2,v.end());
      }while(next_permutation(v.begin(),v.end()));*/