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

#include <bits/stdc++.h>

using namespace std;

// #define INF 1001000100010001000
#define INF 1010001000
#define MOD 1000000007
#define EPS 1e-10
// #define int long long
#define rep(i, N) for (int i = 0; i < N; i++)
#define Rep(i, N) for (int i = 1; i < N; i++)
#define For(i, a, b) for (int i = (a); i < (b); i++)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define pii pair<int, int>
#define vi vector<int>
#define vvi vector<vi>
#define vb vector<bool>
#define vvb vector<vb>
#define vp vector<pii>
#define all(a) (a).begin(), (a).end()
#define Int(x)                                                                 \\
  int x;                                                                       \\
  cin >> x;
#define int2(x, y)                                                             \\
  Int(x);                                                                      \\
  Int(y);
#define int3(x, y, z)                                                          \\
  Int(x);                                                                      \\
  int2(y, z);
#define in(x, a, b) ((a) <= (x) && (x) < (b))
#define fir first
#define sec second
#define ffir first.first
#define fsec first.second
#define sfir second.first
#define ssec second.second
#define Decimal fixed << setprecision(10)

// int dxy[5] = {0, 1, 0, -1, 0};
//  cmd

signed main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);

  string st;
  cin >> st;

  vvi dp(2, vi(2019, 0));

  int ans = 0;
  rep(i, st.size()) {
    rep(j, 2019) {
      dp[!(i & 1)][(j * 10 + (st[i] - '0')) % 2019] = dp[i & 1][j];
    }
    dp[!(i & 1)][(st[i] - '0')]++;
    ans += dp[!(i & 1)][0];
  }

  cout << ans << endl;

  return 0;
}


Error: MLE

Fixed submission:

#include <bits/stdc++.h>

using namespace std;

// #define INF 1001000100010001000
#define INF 1010001000
#define MOD 1000000007
#define EPS 1e-10
// #define int long long
#define rep(i, N) for (int i = 0; i < N; i++)
#define Rep(i, N) for (int i = 1; i < N; i++)
#define For(i, a, b) for (int i = (a); i < (b); i++)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define pii pair<int, int>
#define vi vector<int>
#define vvi vector<vi>
#define vb vector<bool>
#define vvb vector<vb>
#define vp vector<pii>
#define all(a) (a).begin(), (a).end()
#define Int(x)                                                                 \\
  int x;                                                                       \\
  cin >> x;
#define int2(x, y)                                                             \\
  Int(x);                                                                      \\
  Int(y);
#define int3(x, y, z)                                                          \\
  Int(x);                                                                      \\
  int2(y, z);
#define in(x, a, b) ((a) <= (x) && (x) < (b))
#define fir first
#define sec second
#define ffir first.first
#define fsec first.second
#define sfir second.first
#define ssec second.second
#define Decimal fixed << setprecision(10)

// int dxy[5] = {0, 1, 0, -1, 0};
//  cmd

signed main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);

  string st;
  cin >> st;

  vvi dp(st.size() + 1, vi(2019, 0));

  int ans = 0;
  rep(i, st.size()) {
    rep(j, 2019) { dp[i + 1][(j * 10 + (st[i] - '0')) % 2019] += dp[i][j]; }
    dp[i + 1][(st[i] - '0')]++;
    ans += dp[i + 1][0];
  }

  cout << ans << endl;

  return 0;
}