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

// #define NDEBUG
#include "bits/stdc++.h"
#include <array>
#include <iostream>
#include <random>
#include <string>
#include <unordered_map>
#include <unordered_set>
#ifdef _MSC_VER
#include <ppl.h>
// #include <boost/multiprecision/cpp_dec_float.hpp>
// #include <boost/multiprecision/cpp_int.hpp>
// #include <boost/rational.hpp>
// #include <opencv2/core.hpp>
// #include <opencv2/imgproc.hpp>
// #include <opencv2/highgui.hpp>
// #else
// #include <omp.h>
#endif

using namespace std;

#define DUMPOUT cerr
#define dump(...)                                                              \\
  DUMPOUT << "  ";                                                             \\
  DUMPOUT << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]"   \\
          << endl;                                                             \\
  DUMPOUT << "    ";                                                           \\
  dump_func(__VA_ARGS__)

using uint = unsigned;
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pdd = pair<double, double>;
using pss = pair<string, string>;
template <typename _KTy, typename _Ty>
ostream &operator<<(ostream &o, const pair<_KTy, _Ty> &m) {
  o << "{" << m.first << ", " << m.second << "}";
  return o;
}
template <typename _KTy, typename _Ty>
ostream &operator<<(ostream &o, const map<_KTy, _Ty> &m) {
  if (m.empty()) {
    o << "{ }";
    return o;
  }
  o << "{" << *m.begin();
  for (auto itr = ++m.begin(); itr != m.end(); itr++) {
    o << ", " << *itr;
  }
  o << "}";
  return o;
}
template <typename _KTy, typename _Ty>
ostream &operator<<(ostream &o, const unordered_map<_KTy, _Ty> &m) {
  if (m.empty()) {
    o << "{ }";
    return o;
  }
  o << "{" << *m.begin();
  for (auto itr = ++m.begin(); itr != m.end(); itr++) {
    o << ", " << *itr;
  }
  o << "}";
  return o;
}
template <typename _Ty> ostream &operator<<(ostream &o, const vector<_Ty> &v) {
  if (v.empty()) {
    o << "{ }";
    return o;
  }
  o << "{" << v.front();
  for (auto itr = ++v.begin(); itr != v.end(); itr++) {
    o << ", " << *itr;
  }
  o << "}";
  return o;
}
template <typename _Ty> ostream &operator<<(ostream &o, const deque<_Ty> &v) {
  if (v.empty()) {
    o << "{ }";
    return o;
  }
  o << "{" << v.front();
  for (auto itr = ++v.begin(); itr != v.end(); itr++) {
    o << ", " << *itr;
  }
  o << "}";
  return o;
}
template <typename _Ty> ostream &operator<<(ostream &o, const set<_Ty> &s) {
  if (s.empty()) {
    o << "{ }";
    return o;
  }
  o << "{" << *(s.begin());
  for (auto itr = ++s.begin(); itr != s.end(); itr++) {
    o << ", " << *itr;
  }
  o << "}";
  return o;
}
template <typename _Ty>
ostream &operator<<(ostream &o, const unordered_set<_Ty> &s) {
  if (s.empty()) {
    o << "{ }";
    return o;
  }
  o << "{" << *(s.begin());
  for (auto itr = ++s.begin(); itr != s.end(); itr++) {
    o << ", " << *itr;
  }
  o << "}";
  return o;
}
template <typename _Ty> ostream &operator<<(ostream &o, const stack<_Ty> &s) {
  if (s.empty()) {
    o << "{ }";
    return o;
  }
  stack<_Ty> t(s);
  o << "{" << t.top();
  t.pop();
  while (!t.empty()) {
    o << ", " << t.top();
    t.pop();
  }
  o << "}";
  return o;
}
template <typename _Ty> ostream &operator<<(ostream &o, const list<_Ty> &l) {
  if (l.empty()) {
    o << "{ }";
    return o;
  }
  o << "{" << l.front();
  for (auto itr = ++l.begin(); itr != l.end(); ++itr) {
    o << ", " << *itr;
  }
  o << "}";
  return o;
}
template <typename _KTy, typename _Ty>
istream &operator>>(istream &is, pair<_KTy, _Ty> &m) {
  is >> m.first >> m.second;
  return is;
}
template <typename _Ty> istream &operator>>(istream &is, vector<_Ty> &v) {
  for (size_t t = 0; t < v.size(); t++)
    is >> v[t];
  return is;
}
template <typename _Ty> istream &operator>>(istream &is, deque<_Ty> &v) {
  for (size_t t = 0; t < v.size(); t++)
    is >> v[t];
  return is;
}
namespace aux { // print tuple
template <typename Ty, unsigned N, unsigned L> struct tp {
  static void print(ostream &os, const Ty &v) {
    os << get<N>(v) << ", ";
    tp<Ty, N + 1, L>::print(os, v);
  }
};
template <typename Ty, unsigned N> struct tp<Ty, N, N> {
  static void print(ostream &os, const Ty &v) { os << get<N>(v); }
};
} // namespace aux

template <typename... Tys>
ostream &operator<<(ostream &os, const tuple<Tys...> &t) {
  os << "{";
  aux::tp<tuple<Tys...>, 0, sizeof...(Tys) - 1>::print(os, t);
  os << "}";
  return os;
}

template <typename A, size_t N, typename T>
inline void Fill(A (&array)[N], const T &val) {
  fill((T *)array, (T *)(array + N), val);
}

void dump_func() { DUMPOUT << endl; }
template <class Head, class... Tail>
void dump_func(Head &&head, Tail &&...tail) {
  DUMPOUT << head;
  if (sizeof...(Tail) == 0) {
    DUMPOUT << " ";
  } else {
    DUMPOUT << ", ";
  }
  dump_func(move(tail)...);
}

#define PI 3.14159265358979323846
#define EPS 1e-8
#define rep(t, n) for (int t = 0; t < (n); ++t)
#define all(j) (j).begin(), (j).end()
#define SZ(j) ((int)(j).size())
#define fake false

class Timer {
public:
  double t = 0;
  Timer() {}
  static double time() {
#ifdef _MSC_VER
    return __rdtsc() / 2.8e9;
#else
    unsigned long long a, d;
    __asm__ volatile("rdtsc" : "=a"(a), "=d"(d));
    return (d << 32 | a) / 2.8e9;
#endif
  }
  void measure() { t = time() - t; }
  double elapsedMs() { return (time() - t) * 1000.0; }
} timer;

struct Xorshift {
  uint64_t x = 88172645463325252LL;
  unsigned next_int() {
    x = x ^ (x << 7);
    return x = x ^ (x >> 9);
  }
  unsigned next_int(unsigned mod) {
    x = x ^ (x << 7);
    x = x ^ (x >> 9);
    return x % mod;
  }
  unsigned next_int(unsigned l, unsigned r) {
    x = x ^ (x << 7);
    x = x ^ (x >> 9);
    return x % (r - l + 1) + l;
  }
  double next_double() { return double(next_int()) / UINT_MAX; }
} rnd;

template <typename T> void shuffle_vector(vector<T> &v, Xorshift &rnd) {
  int n = v.size();
  for (int i = n - 1; i >= 1; i--) {
    int r = rnd.next_int(i);
    swap(v[i], v[r]);
  }
}

int main() {
  timer.measure();

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

  string S;
  cin >> S;
  // rep(i, 200000) S.push_back(rnd.next_int(9) + 1 + '0');

  ll ans = 0;
  int cnt[2019] = {};
  cnt[S[0] - '0']++;
  for (int i = 1; i < S.size(); i++) {
    // if (i % 1000 == 0) cerr << i << endl;
    int ncnt[2019] = {};
    int d = S[i] - '0';
    for (int j = 0; j < 2019; j++) {
      if (cnt[j]) {
        ncnt[(j * 10 + d) % 2019] += cnt[j];
      }
    }
    ncnt[d]++;
    ans += ncnt[0];
    memcpy(cnt, ncnt, sizeof(int) * 2019);
  }

  cout << ans << endl;

  return 0;
}


Error: TLE

Fixed submission:

// #define NDEBUG
#include "bits/stdc++.h"
#include <array>
#include <iostream>
#include <random>
#include <string>
#include <unordered_map>
#include <unordered_set>
#ifdef _MSC_VER
#include <ppl.h>
// #include <boost/multiprecision/cpp_dec_float.hpp>
// #include <boost/multiprecision/cpp_int.hpp>
// #include <boost/rational.hpp>
// #include <opencv2/core.hpp>
// #include <opencv2/imgproc.hpp>
// #include <opencv2/highgui.hpp>
// #else
// #include <omp.h>
#endif

using namespace std;

#define DUMPOUT cerr
#define dump(...)                                                              \\
  DUMPOUT << "  ";                                                             \\
  DUMPOUT << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]"   \\
          << endl;                                                             \\
  DUMPOUT << "    ";                                                           \\
  dump_func(__VA_ARGS__)

using uint = unsigned;
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pdd = pair<double, double>;
using pss = pair<string, string>;
template <typename _KTy, typename _Ty>
ostream &operator<<(ostream &o, const pair<_KTy, _Ty> &m) {
  o << "{" << m.first << ", " << m.second << "}";
  return o;
}
template <typename _KTy, typename _Ty>
ostream &operator<<(ostream &o, const map<_KTy, _Ty> &m) {
  if (m.empty()) {
    o << "{ }";
    return o;
  }
  o << "{" << *m.begin();
  for (auto itr = ++m.begin(); itr != m.end(); itr++) {
    o << ", " << *itr;
  }
  o << "}";
  return o;
}
template <typename _KTy, typename _Ty>
ostream &operator<<(ostream &o, const unordered_map<_KTy, _Ty> &m) {
  if (m.empty()) {
    o << "{ }";
    return o;
  }
  o << "{" << *m.begin();
  for (auto itr = ++m.begin(); itr != m.end(); itr++) {
    o << ", " << *itr;
  }
  o << "}";
  return o;
}
template <typename _Ty> ostream &operator<<(ostream &o, const vector<_Ty> &v) {
  if (v.empty()) {
    o << "{ }";
    return o;
  }
  o << "{" << v.front();
  for (auto itr = ++v.begin(); itr != v.end(); itr++) {
    o << ", " << *itr;
  }
  o << "}";
  return o;
}
template <typename _Ty> ostream &operator<<(ostream &o, const deque<_Ty> &v) {
  if (v.empty()) {
    o << "{ }";
    return o;
  }
  o << "{" << v.front();
  for (auto itr = ++v.begin(); itr != v.end(); itr++) {
    o << ", " << *itr;
  }
  o << "}";
  return o;
}
template <typename _Ty> ostream &operator<<(ostream &o, const set<_Ty> &s) {
  if (s.empty()) {
    o << "{ }";
    return o;
  }
  o << "{" << *(s.begin());
  for (auto itr = ++s.begin(); itr != s.end(); itr++) {
    o << ", " << *itr;
  }
  o << "}";
  return o;
}
template <typename _Ty>
ostream &operator<<(ostream &o, const unordered_set<_Ty> &s) {
  if (s.empty()) {
    o << "{ }";
    return o;
  }
  o << "{" << *(s.begin());
  for (auto itr = ++s.begin(); itr != s.end(); itr++) {
    o << ", " << *itr;
  }
  o << "}";
  return o;
}
template <typename _Ty> ostream &operator<<(ostream &o, const stack<_Ty> &s) {
  if (s.empty()) {
    o << "{ }";
    return o;
  }
  stack<_Ty> t(s);
  o << "{" << t.top();
  t.pop();
  while (!t.empty()) {
    o << ", " << t.top();
    t.pop();
  }
  o << "}";
  return o;
}
template <typename _Ty> ostream &operator<<(ostream &o, const list<_Ty> &l) {
  if (l.empty()) {
    o << "{ }";
    return o;
  }
  o << "{" << l.front();
  for (auto itr = ++l.begin(); itr != l.end(); ++itr) {
    o << ", " << *itr;
  }
  o << "}";
  return o;
}
template <typename _KTy, typename _Ty>
istream &operator>>(istream &is, pair<_KTy, _Ty> &m) {
  is >> m.first >> m.second;
  return is;
}
template <typename _Ty> istream &operator>>(istream &is, vector<_Ty> &v) {
  for (size_t t = 0; t < v.size(); t++)
    is >> v[t];
  return is;
}
template <typename _Ty> istream &operator>>(istream &is, deque<_Ty> &v) {
  for (size_t t = 0; t < v.size(); t++)
    is >> v[t];
  return is;
}
namespace aux { // print tuple
template <typename Ty, unsigned N, unsigned L> struct tp {
  static void print(ostream &os, const Ty &v) {
    os << get<N>(v) << ", ";
    tp<Ty, N + 1, L>::print(os, v);
  }
};
template <typename Ty, unsigned N> struct tp<Ty, N, N> {
  static void print(ostream &os, const Ty &v) { os << get<N>(v); }
};
} // namespace aux

template <typename... Tys>
ostream &operator<<(ostream &os, const tuple<Tys...> &t) {
  os << "{";
  aux::tp<tuple<Tys...>, 0, sizeof...(Tys) - 1>::print(os, t);
  os << "}";
  return os;
}

template <typename A, size_t N, typename T>
inline void Fill(A (&array)[N], const T &val) {
  fill((T *)array, (T *)(array + N), val);
}

void dump_func() { DUMPOUT << endl; }
template <class Head, class... Tail>
void dump_func(Head &&head, Tail &&...tail) {
  DUMPOUT << head;
  if (sizeof...(Tail) == 0) {
    DUMPOUT << " ";
  } else {
    DUMPOUT << ", ";
  }
  dump_func(move(tail)...);
}

#define PI 3.14159265358979323846
#define EPS 1e-8
#define rep(t, n) for (int t = 0; t < (n); ++t)
#define all(j) (j).begin(), (j).end()
#define SZ(j) ((int)(j).size())
#define fake false

class Timer {
public:
  double t = 0;
  Timer() {}
  static double time() {
#ifdef _MSC_VER
    return __rdtsc() / 2.8e9;
#else
    unsigned long long a, d;
    __asm__ volatile("rdtsc" : "=a"(a), "=d"(d));
    return (d << 32 | a) / 2.8e9;
#endif
  }
  void measure() { t = time() - t; }
  double elapsedMs() { return (time() - t) * 1000.0; }
} timer;

struct Xorshift {
  uint64_t x = 88172645463325252LL;
  unsigned next_int() {
    x = x ^ (x << 7);
    return x = x ^ (x >> 9);
  }
  unsigned next_int(unsigned mod) {
    x = x ^ (x << 7);
    x = x ^ (x >> 9);
    return x % mod;
  }
  unsigned next_int(unsigned l, unsigned r) {
    x = x ^ (x << 7);
    x = x ^ (x >> 9);
    return x % (r - l + 1) + l;
  }
  double next_double() { return double(next_int()) / UINT_MAX; }
} rnd;

template <typename T> void shuffle_vector(vector<T> &v, Xorshift &rnd) {
  int n = v.size();
  for (int i = n - 1; i >= 1; i--) {
    int r = rnd.next_int(i);
    swap(v[i], v[r]);
  }
}

int main() {
  timer.measure();

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

  string S;
  cin >> S;
  // rep(i, 200000) S.push_back(rnd.next_int(9) + 1 + '0');

  ll ans = 0;
  unordered_map<int, int> cnt;
  cnt[S[0] - '0']++;
  for (int i = 1; i < S.size(); i++) {
    unordered_map<int, int> ncnt;
    int d = S[i] - '0';
    for (auto e : cnt) {
      ncnt[(e.first * 10 + d) % 2019] += e.second;
    }
    ncnt[d]++;
    cnt = ncnt;
    // dump(cnt);
    ans += cnt[0];
  }

  cout << ans << endl;

  return 0;
}