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

#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int INF = 1e9;
const ll LINF = 1e18;
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
template <class S, class T>
ostream &operator<<(ostream &out, const pair<S, T> &o) {
  out << "(" << o.first << "," << o.second << ")";
  return out;
}
template <class T> ostream &operator<<(ostream &out, const vector<T> &V) {
  for (int i = 0; i < V.size(); i++) {
    out << V[i];
    if (i != V.size() - 1)
      out << " ";
  }
  return out;
}
template <class T>
ostream &operator<<(ostream &out, const vector<vector<T>> &Mat) {
  for (int i = 0; i < Mat.size(); i++) {
    if (i != 0)
      out << endl;
    out << Mat[i];
  }
  return out;
}
template <class S, class T>
ostream &operator<<(ostream &out, const map<S, T> &mp) {
  out << "{ ";
  for (auto it = mp.begin(); it != mp.end(); it++) {
    out << it->first << ":" << it->second;
    if (mp.size() - 1 != distance(mp.begin(), it))
      out << ", ";
  }
  out << " }";
  return out;
}
template <typename T> vector<T> make_v(size_t a) { return vector<T>(a); }
template <typename T, typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}
template <typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type fill_v(T &t, const V &v) {
  t = v;
}
template <typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type fill_v(T &t, const V &v) {
  for (auto &e : t)
    fill_v(e, v);
}
/*
 <url:>
 問題文============================================================
 =================================================================
 解説=============================================================
 ================================================================
 */

template <class Type> Type solve(Type res = Type()) {
  string S;
  cin >> S;
  int N = (int)S.length();

  //    auto dp = make_v<ll>(N+1,2019);
  //    for(int i = 0; i < N;i++){
  //        for(int j = 0; j < 2019;j++){
  //            if(dp[i][j] == 0) continue;
  //            dp[i+1][(j*10+S[i]-'0')%2019] += dp[i][j];
  //        }
  //        res += dp[i][0];
  //        dp[i+1][S[i]-'0']++;
  //    }
  //    res += dp[N][0];

  reverse(S.begin(), S.end());

  vector<ll> base(N + 1);
  base[0] = 1;
  for (int i = 0; i < N; i++) {
    base[i + 1] = base[i] * 10 % 2019;
  }
  vector<ll> cusum(N + 1);
  map<ll, ll> mp;
  for (int i = 0; i < N; i++) {
    mp[cusum[i]]++;

    cusum[i + 1] = (S[i] - '0') * base[i] + cusum[i];
    cusum[i + 1] %= 2019;

    res += mp[cusum[i + 1]];
  }
  return res;
}
int main(void) {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  // solve(0);
  cout << fixed << setprecision(15) << solve<ll>() << endl;
  return 0;
}


Error: TLE

Fixed submission:

#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int INF = 1e9;
const ll LINF = 1e18;
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
template <class S, class T>
ostream &operator<<(ostream &out, const pair<S, T> &o) {
  out << "(" << o.first << "," << o.second << ")";
  return out;
}
template <class T> ostream &operator<<(ostream &out, const vector<T> &V) {
  for (int i = 0; i < V.size(); i++) {
    out << V[i];
    if (i != V.size() - 1)
      out << " ";
  }
  return out;
}
template <class T>
ostream &operator<<(ostream &out, const vector<vector<T>> &Mat) {
  for (int i = 0; i < Mat.size(); i++) {
    if (i != 0)
      out << endl;
    out << Mat[i];
  }
  return out;
}
template <class S, class T>
ostream &operator<<(ostream &out, const map<S, T> &mp) {
  out << "{ ";
  for (auto it = mp.begin(); it != mp.end(); it++) {
    out << it->first << ":" << it->second;
    if (mp.size() - 1 != distance(mp.begin(), it))
      out << ", ";
  }
  out << " }";
  return out;
}
template <typename T> vector<T> make_v(size_t a) { return vector<T>(a); }
template <typename T, typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}
template <typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type fill_v(T &t, const V &v) {
  t = v;
}
template <typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type fill_v(T &t, const V &v) {
  for (auto &e : t)
    fill_v(e, v);
}
/*
 <url:>
 問題文============================================================
 =================================================================
 解説=============================================================
 ================================================================
 */

template <class Type> Type solve(Type res = Type()) {
  string S;
  cin >> S;
  int N = (int)S.length();

  auto dp = make_v<ll>(N + 1, 2019);
  for (int i = 0; i < N; i++) {
    for (int j = 0; j < 2019; j++) {
      if (dp[i][j] == 0)
        continue;
      dp[i + 1][(j * 10 + S[i] - '0') % 2019] += dp[i][j];
    }
    res += dp[i][0];
    dp[i + 1][S[i] - '0']++;
  }
  res += dp[N][0];
  return res;
}
int main(void) {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  // solve(0);
  cout << fixed << setprecision(15) << solve<ll>() << endl;
  return 0;
}