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

//----AUTHOR:kkdrummer----/
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
typedef long long ll;
typedef long double ld;
// typedef    unordered_set<ll>   usll;
// typedef    unordered_multiset<ll>   umsll;
typedef multiset<ll> msll;
typedef set<ll> sll;
typedef vector<ll> vll;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef priority_queue<ll> pqll;
typedef vector<int> vi;
typedef set<int> si;
typedef multiset<int> msi;
// typedef    unordered_multiset<int>   umsi;
// typedef    unordered_set<int>   usi;
typedef pair<int, int> pi;
typedef vector<pi> vpi;
typedef set<pi> spi;
typedef priority_queue<int> pqi;
typedef tree<int, null_type, less<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    ind_set;
typedef tree<ll, null_type, less<ll>, rb_tree_tag,
             tree_order_statistics_node_update>
    ind_setll;
#define in insert
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define be begin
#define en end
#define itr iterator
#define io                                                                     \\
  ios_base::sync_with_stdio(false);                                            \\
  cin.tie(NULL);                                                               \\
  cout.tie(NULL);
#define mo 2019
#define inf 9223372036854775807
#define ninf -inf
#define ima 2147483647
#define imi -ima
#define oncnt __builtin_popcount
#define zerobegin __builtin_clz
#define zeroend __builtin_ctz
#define parity __builtin_parity
#define all(x) x.be(), x.en()
#define eps 1e-9
#define coutd cout << setprecision(10) << fixed
#define mems(dp, x) memset(dp, x, sizeof(dp))
const ld PI = 3.1415926535897932384626433832792884197169399375105820974944;
inline ll modpow(ll x, ll n) {
  if (n == 0)
    return 1;
  if (n == 1)
    return (x % mo);
  ll u = (modpow(x, n / 2));
  u = (u * u) % mo;
  if (n % 2 != 0)
    u = (u * x % mo) % mo;
  return u;
}
inline ll modinv(ll x) { return modpow(x, mo - 2); }
inline ll mmul(ll a, ll b) {
  if (a >= mo)
    a = a % mo;
  if (b >= mo)
    b = b % mo;
  if (a * b >= mo)
    return (a * b) % mo;
  return (a * b);
}
inline ll madd(ll a, ll b) {
  if (a >= mo)
    a = a % mo;
  if (b >= mo)
    b = b % mo;
  if (a + b >= mo)
    return (a + b) % mo;
  return (a + b);
}
inline ll msub(ll a, ll b) {
  if (a >= mo)
    a = a % mo;
  if (b >= mo)
    b = b % mo;
  return (((a - b) % mo + mo) % mo);
}
inline ll mdiv(ll a, ll bb) {
  if (a >= mo)
    a = a % mo;
  ll b = modinv(bb);
  if (b >= mo)
    b = b % mo;
  if (a * b >= mo)
    return (a * b) % mo;
  return (a * b);
}
inline ll gcd(ll a, ll b) { return __gcd(a, b); }
inline int lcm(int a, int b) { return ((a * b) / gcd(a, b)); }

int main() {
  io int testcases = 1; // cin>>testcases;
  while (testcases--) {

    string s;
    cin >> s;
    int n = s.length();

    ll pro = 1;
    ll cur = 0;
    ll dp[2019] = {0};
    dp[cur]++;
    for (int i = 0; i < n; i++) {
      ll ne = s[n - i - 1] - '0';
      cur = (cur + (pro * ne)) % 2019;
      pro = mmul(pro, 10);
      dp[cur]++;
    }

    ll ans = 0;

    for (int i = 0; i < 2019; i++) {
      ll m = dp[i];
      ans += ((m * (m - 1)) / 2);
    }

    cout << ans;
  }
  return 0;
}

Error: TLE

Fixed submission:

//----AUTHOR:kkdrummer----/
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
typedef long long ll;
typedef long double ld;
// typedef    unordered_set<ll>   usll;
// typedef    unordered_multiset<ll>   umsll;
typedef multiset<ll> msll;
typedef set<ll> sll;
typedef vector<ll> vll;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef priority_queue<ll> pqll;
typedef vector<int> vi;
typedef set<int> si;
typedef multiset<int> msi;
// typedef    unordered_multiset<int>   umsi;
// typedef    unordered_set<int>   usi;
typedef pair<int, int> pi;
typedef vector<pi> vpi;
typedef set<pi> spi;
typedef priority_queue<int> pqi;
typedef tree<int, null_type, less<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    ind_set;
typedef tree<ll, null_type, less<ll>, rb_tree_tag,
             tree_order_statistics_node_update>
    ind_setll;
#define in insert
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define be begin
#define en end
#define itr iterator
#define io                                                                     \\
  ios_base::sync_with_stdio(false);                                            \\
  cin.tie(NULL);                                                               \\
  cout.tie(NULL);
#define mo 1000000007
#define inf 9223372036854775807
#define ninf -inf
#define ima 2147483647
#define imi -ima
#define oncnt __builtin_popcount
#define zerobegin __builtin_clz
#define zeroend __builtin_ctz
#define parity __builtin_parity
#define all(x) x.be(), x.en()
#define eps 1e-9
#define coutd cout << setprecision(10) << fixed
#define mems(dp, x) memset(dp, x, sizeof(dp))
const ld PI = 3.14159265359;
inline ll modpow(ll x, ll n) {
  if (n == 0)
    return 1;
  if (n == 1)
    return (x % mo);
  ll u = (modpow(x, n / 2));
  u = (u * u) % mo;
  if (n % 2 != 0)
    u = (u * x % mo) % mo;
  return u;
}
inline ll modinv(ll x) { return modpow(x, mo - 2); }
inline ll mmul(ll a, ll b) {
  if (a >= mo)
    a = a % mo;
  if (b >= mo)
    b = b % mo;
  if (a * b >= mo)
    return (a * b) % mo;
  return (a * b);
}
inline ll madd(ll a, ll b) {
  if (a >= mo)
    a = a % mo;
  if (b >= mo)
    b = b % mo;
  if (a + b >= mo)
    return (a + b) % mo;
  return (a + b);
}
inline ll msub(ll a, ll b) {
  if (a >= mo)
    a = a % mo;
  if (b >= mo)
    b = b % mo;
  return (((a - b) % mo + mo) % mo);
}
inline ll mdiv(ll a, ll bb) {
  if (a >= mo)
    a = a % mo;
  ll b = modinv(bb);
  if (b >= mo)
    b = b % mo;
  if (a * b >= mo)
    return (a * b) % mo;
  return (a * b);
}
inline ll gcd(ll a, ll b) { return __gcd(a, b); }

bool eval(string s) {
  int h = 0;
  int cur = 0;
  for (int i = 0; i < s.length(); i++) {
    h = ((cur * 10) + (s[i] - '0')) % 2019;
    cur = h;
  }
  if (h == 0)
    return true;
  return false;
}

int main() {
  io int testcases = 1; // cin>>testcases;
  while (testcases--) {

    string s;
    cin >> s;
    if (s.length() < 5)
      cout << 0;

    else {
      int n = s.length();
      int c = 0;
      int l = 5;
      while (l <= n) {
        int i = 0;
        int k = 1;
        while (i <= n - l) {
          string ss = s.substr(i, l);
          if (eval(ss)) {
            c++;
            k = (l - 1);
          }

          i += k;
        }
        l++;
      }

      cout << c;
    }
  }
  return 0;
}