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

#include <bits/stdc++.h>
using namespace std;

// TO_STRING
template <typename A, typename B> string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string &s) { return '"' + s + '"'; }

string to_string(char ch) {
  string s;
  s += ch;
  return s;
}

string to_string(const char *s) { return to_string((string)s); }

string to_string(bool b) { return (b ? "true" : "false"); }

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N> string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

// DEBUG
void debug_out() { cerr << endl; }

template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL // compile with -DLOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pll;

typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<bool> vb;
typedef vector<pi> vpi;
typedef vector<char> vch;
typedef vector<string> vstr;
typedef vector<vi> vvi;
typedef vector<vpi> vvpi;
typedef vector<pll> vpll;
typedef vector<vll> vvll;
typedef vector<vb> vvb;
typedef vector<vvi> vvvi;
typedef vector<vch> vvch;
typedef vector<vstr> vvstr;

#define all(x) x.begin(), x.end()
#define pb push_back
#define pf push_front
#define fi first
#define se second
#define sz(x) ((ll)x.size())

void solve() {
  string s;
  cin >> s;
  int n = sz(s);
  const int m = 2019;
  vvi dp(2, vi(m));
  dp[0][s[0] - '0'] = 1;
  int bit = 0;
  ll ans = dp[0][0];

  for (int i = 0; i < n - 1; i++) {
    int next_bit = bit ^ 1;

    dp[next_bit][s[i + 1] - '0']++;
    for (int rim = 0; rim < m; rim++) {
      int next = rim * 10 + (s[i + 1] - '0');
      next %= m;
      dp[next_bit][next] += dp[bit][rim];
      dp[bit][rim] = 0;
    }
    ans += dp[next_bit][0];
    debug(next_bit, ans);
    bit = next_bit;
  }
  // debug(dp);
  cout << ans << endl;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);

  int t = 1;
  for (int tc = 1; tc <= t; tc++) {
    solve();
  }
}

Error: MLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;

// TO_STRING
template <typename A, typename B> string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string &s) { return '"' + s + '"'; }

string to_string(char ch) {
  string s;
  s += ch;
  return s;
}

string to_string(const char *s) { return to_string((string)s); }

string to_string(bool b) { return (b ? "true" : "false"); }

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N> string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

// DEBUG
void debug_out() { cerr << endl; }

template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL // compile with -DLOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pll;

typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<bool> vb;
typedef vector<pi> vpi;
typedef vector<char> vch;
typedef vector<string> vstr;
typedef vector<vi> vvi;
typedef vector<vpi> vvpi;
typedef vector<pll> vpll;
typedef vector<vll> vvll;
typedef vector<vb> vvb;
typedef vector<vvi> vvvi;
typedef vector<vch> vvch;
typedef vector<vstr> vvstr;

#define all(x) x.begin(), x.end()
#define pb push_back
#define pf push_front
#define fi first
#define se second
#define sz(x) ((ll)x.size())

void solve() {
  string s;
  cin >> s;
  int n = sz(s);
  const int m = 2019;
  vvi dp(n, vi(m));
  dp[0][s[0] - '0'] = 1;
  for (int i = 0; i < n - 1; i++) {
    dp[i + 1][s[i + 1] - '0']++;
    for (int rim = 0; rim < m; rim++) {
      int next = rim * 10 + (s[i + 1] - '0');
      next %= m;
      dp[i + 1][next] += dp[i][rim];
    }
  }
  ll ans = 0;
  for (int i = 0; i < n; i++) {
    ans += dp[i][0];
  }
  cout << ans << endl;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);

  int t = 1;
  for (int tc = 1; tc <= t; tc++) {
    solve();
  }
}