Problem p02618 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
using namespace std;
#pragma region Macros
typedef long long ll;
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) (x).begin(), (x).end()
const long long MOD = 1e9 + 7;
// const long long MOD=998244353;
const int INF = 1e9;
const long long IINF = 1e18;
const int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const char dir[4] = {'D', 'R', 'U', 'L'};
#define LOCAL

template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &x : v)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < v.size(); ++i) {
    os << v[i] << (i + 1 == v.size() ? "" : " ");
  }
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  cout << '(' << p.first << ',' << p.second << ')';
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const map<T, U> &m) {
  os << '{';
  for (auto itr = m.begin(); itr != m.end(); ++itr) {
    os << '(' << itr->first << ',' << itr->second << ')';
    if (++itr != m.end())
      os << ',';
    --itr;
  }
  os << '}';
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const set<T> &s) {
  os << '{';
  for (auto itr = s.begin(); itr != s.end(); ++itr) {
    os << *itr;
    if (++itr != s.end())
      os << ',';
    --itr;
  }
  os << '}';
  return os;
}

void debug_out() { cerr << '\\n'; }
template <class Head, class... Tail>
void debug_out(Head &&head, Tail &&...tail) {
  cerr << head;
  if (sizeof...(Tail) > 0)
    cerr << ", ";
  debug_out(move(tail)...);
}
#ifdef LOCAL
#define debug(...)                                                             \\
  cerr << " ";                                                                 \\
  cerr << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]"      \\
       << '\\n';                                                                \\
  cerr << " ";                                                                 \\
  debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

template <typename T> T gcd(T x, T y) { return y != 0 ? gcd(y, x % y) : x; }
template <typename T> T lcm(T x, T y) { return x / gcd(x, y) * y; }

template <class T1, class T2> inline bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T1, class T2> inline bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
#pragma endregion

int D, M, now = 0;
int c[26], s[370][26], t[370], last[26];
set<int> days[26];

void init() {
  for (int i = 0; i < 26; ++i) {
    days[i].emplace(-1);
    days[i].emplace(D);
    last[i] = -1;
  }
  for (int i = 0; i < D; ++i) {
    now += s[i][t[i]];
    last[t[i]] = i;
    days[t[i]].emplace(i);
    for (int j = 0; j < 26; ++j)
      now -= c[j] * (i - last[j]);
  }
}

int calc(int d, int q) {
  int pre, nxt, old, res = now;
  old = t[d];
  auto itr1 = days[old].lower_bound(d);
  pre = *(--itr1);
  ++itr1;
  nxt = *(++itr1);
  res -= c[old] * (d - pre) * (nxt - d) + s[d][old];
  auto itr2 = days[q].upper_bound(d);
  nxt = *itr2;
  pre = *(--itr2);
  res += c[q] * (d - pre) * (nxt - d) + s[d][q];
  return res;
}

void change(int d, int q) {
  now = calc(d, q);
  int old = t[d];
  days[old].erase(days[old].find(d));
  days[q].emplace(d);
  t[d] = q;
}

void solve() {
  chrono::system_clock::time_point start, end;
  start = chrono::system_clock::now();
  while (1) {
    int d = rand() % D, q = rand() % 26;
    if (t[d] == q)
      continue;
    if (calc(d, q) > now)
      change(d, q);
    end = chrono::system_clock::now();
    double time = static_cast<double>(
        chrono::duration_cast<chrono::microseconds>(end - start).count() /
        1000.0);
    if (time > 1.8e3)
      break;
  }
  for (int i = 0; i < D; ++i)
    cout << t[i] + 1 << '\\n';
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin >> D;
  for (int i = 0; i < 26; ++i)
    cin >> c[i];
  for (int i = 0; i < D; ++i) {
    for (int j = 0; j < 26; ++j) {
      cin >> s[i][j];
    }
  }
  for (int i = 0; i < D; ++i)
    t[i] = i % 26;
  init();
  solve();
}

Error: WA

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
#pragma region Macros
typedef long long ll;
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) (x).begin(), (x).end()
const long long MOD = 1e9 + 7;
// const long long MOD=998244353;
const int INF = 1e9;
const long long IINF = 1e18;
const int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const char dir[4] = {'D', 'R', 'U', 'L'};
#define LOCAL

template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &x : v)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < v.size(); ++i) {
    os << v[i] << (i + 1 == v.size() ? "" : " ");
  }
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  cout << '(' << p.first << ',' << p.second << ')';
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const map<T, U> &m) {
  os << '{';
  for (auto itr = m.begin(); itr != m.end(); ++itr) {
    os << '(' << itr->first << ',' << itr->second << ')';
    if (++itr != m.end())
      os << ',';
    --itr;
  }
  os << '}';
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const set<T> &s) {
  os << '{';
  for (auto itr = s.begin(); itr != s.end(); ++itr) {
    os << *itr;
    if (++itr != s.end())
      os << ',';
    --itr;
  }
  os << '}';
  return os;
}

void debug_out() { cerr << '\\n'; }
template <class Head, class... Tail>
void debug_out(Head &&head, Tail &&...tail) {
  cerr << head;
  if (sizeof...(Tail) > 0)
    cerr << ", ";
  debug_out(move(tail)...);
}
#ifdef LOCAL
#define debug(...)                                                             \\
  cerr << " ";                                                                 \\
  cerr << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]"      \\
       << '\\n';                                                                \\
  cerr << " ";                                                                 \\
  debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

template <typename T> T gcd(T x, T y) { return y != 0 ? gcd(y, x % y) : x; }
template <typename T> T lcm(T x, T y) { return x / gcd(x, y) * y; }

template <class T1, class T2> inline bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T1, class T2> inline bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
#pragma endregion

int D, M, now = 0;
int c[26], s[365][26], t[365], last[26];
set<int> days[26];

void init() {
  for (int i = 0; i < 26; ++i) {
    days[i].emplace(-1);
    days[i].emplace(D);
    last[i] = -1;
  }
  for (int i = 0; i < D; ++i) {
    now += s[i][t[i]];
    last[t[i]] = i;
    days[t[i]].emplace(i);
    for (int j = 0; j < 26; ++j)
      now -= c[j] * (i - last[j]);
  }
}

int calc(int d, int q) {
  int pre, nxt, old, res = now;
  old = t[d];
  auto itr1 = days[old].lower_bound(d);
  pre = *(--itr1);
  ++itr1;
  nxt = *(++itr1);
  res -= c[old] * (d - pre) * (nxt - d) + s[d][old];
  auto itr2 = days[q].upper_bound(d);
  nxt = *itr2;
  pre = *(--itr2);
  res += c[q] * (d - pre) * (nxt - d) + s[d][q];
  return res;
}

void change(int d, int q) {
  now = calc(d, q);
  int old = t[d];
  days[old].erase(days[old].find(d));
  days[q].emplace(d);
  t[d] = q;
}

void solve() {
  chrono::system_clock::time_point start, end;
  start = chrono::system_clock::now();
  while (1) {
    int d = rand() % D, q = rand() % 26;
    if (t[d] == q)
      continue;
    if (calc(d, q) > now)
      change(d, q);
    end = chrono::system_clock::now();
    double time = static_cast<double>(
        chrono::duration_cast<chrono::microseconds>(end - start).count() /
        1000.0);
    if (time > 1.8e3)
      break;
  }
  for (int i = 0; i < D; ++i)
    cout << t[i] + 1 << '\\n';
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin >> D;
  for (int i = 0; i < 26; ++i)
    cin >> c[i];
  for (int i = 0; i < D; ++i) {
    for (int j = 0; j < 26; ++j) {
      cin >> s[i][j];
    }
  }
  for (int i = 0; i < D; ++i)
    t[i] = i;
  init();
  solve();
}