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

/**
 * Created by hiramekun at 20:53 on 2020-04-26.
 */
#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using vl = vector<ll>;
using vvl = vector<vl>;
using vb = vector<bool>;
using P = pair<ll, ll>;
template <typename T> using pq = priority_queue<T>;
template <typename T> using minpq = priority_queue<T, vector<T>, greater<T>>;
template <typename T, typename K> using ump = unordered_map<T, K>;
const ll dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const ll mod = 1000000007;
const ll inf = ll(1e9);
const ll e5 = ll(1e5);
const ll ll_inf = ll(1e9) * ll(1e9);

#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define repr(i, n) for (ll i = ll(n - 1); i >= 0; i--)
#define each(i, mp) for (auto &i : mp)
#define eb emplace_back
#define F first
#define S second
#define all(obj) (obj).begin(), (obj).end()

template <class T> ostream &operator<<(ostream &out, const vector<T> &list) {
  ll n = list.size();
  rep(i, n) out << list[i] << ' ';
  return out;
}

template <class T> istream &operator>>(istream &in, vector<T> &list) {
  ll n = list.size();
  rep(i, n) in >> list[i];
  return in;
}

template <class T>
ostream &operator<<(ostream &out, const vector<vector<T>> &list) {
  ll n = list.size();
  rep(i, n) out << list[i] << '\\n';
  return out;
}

/* ------------- ANSWER ------------- */
/* ---------------------------------- */

void solve() {
  string s;
  cin >> s;
  ll now = 0;
  map<ll, ll> mp;
  mp[0] = 1;
  reverse(all(s));
  ll ten = 1;
  rep(i, s.size()) {
    now = (now + (s[i] - '0') * ten) % 2019;
    ten *= 10;
    ten %= 2019;
    mp[now]++;
  }
  ll ans = 0;
  each(e, mp) { ans += e.S * (e.S - 1) / 2; }
  cout << ans << '\\n';
}

int main() {
#ifdef MY_DEBUG
  while (true) {
#endif
    solve();
#ifdef MY_DEBUG
  }
#endif
  return 0;
}

Error: TLE

Fixed submission:

/**
 * Created by hiramekun at 20:53 on 2020-04-26.
 */
#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using vl = vector<ll>;
using vvl = vector<vl>;
using vb = vector<bool>;
using P = pair<ll, ll>;
template <typename T> using pq = priority_queue<T>;
template <typename T> using minpq = priority_queue<T, vector<T>, greater<T>>;
template <typename T, typename K> using ump = unordered_map<T, K>;
const ll dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const ll mod = 1000000007;
const ll inf = ll(1e9);
const ll e5 = ll(1e5);
const ll ll_inf = ll(1e9) * ll(1e9);

#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define repr(i, n) for (ll i = ll(n - 1); i >= 0; i--)
#define each(i, mp) for (auto &i : mp)
#define eb emplace_back
#define F first
#define S second
#define all(obj) (obj).begin(), (obj).end()

template <class T> ostream &operator<<(ostream &out, const vector<T> &list) {
  ll n = list.size();
  rep(i, n) out << list[i] << ' ';
  return out;
}

template <class T> istream &operator>>(istream &in, vector<T> &list) {
  ll n = list.size();
  rep(i, n) in >> list[i];
  return in;
}

template <class T>
ostream &operator<<(ostream &out, const vector<vector<T>> &list) {
  ll n = list.size();
  rep(i, n) out << list[i] << '\\n';
  return out;
}

/* ------------- ANSWER ------------- */
/* ---------------------------------- */

void solve() {
  string s;
  cin >> s;

  map<ll, ll> mp;
  ll now = 0;
  ll ans = 0;
  rep(i, s.size()) {
    now = now * 10 + (s[i] - '0');
    now %= 2019;
    ump<ll, ll> tmp;
    each(e, mp) {
      mp[(e.F * 10 + (s[i] - '0')) % 2019]++;
      tmp[(e.F * 10 + (s[i] - '0')) % 2019] =
          mp[(e.F * 10 + (s[i] - '0')) % 2019];
    }
    mp[now]++;
    tmp[now] = mp[now];
    ans += tmp[0];

    mp = map<ll, ll>(all(tmp));
  }
  cout << ll(sqrt(ans)) << '\\n';
}

int main() {
#ifdef MY_DEBUG
  while (true) {
#endif
    solve();
#ifdef MY_DEBUG
  }
#endif
  return 0;
}