Problem p02647 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
#include <cassert>
typedef long long int ll;
using namespace std;

// @@ !! LIM(debug)
// --> f:<< debug
// ---- inserted function << from util.cc
template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << "(" << p.first << ", " << p.second << ")";
  return os;
}

template <typename T1, typename T2, typename T3>
ostream &operator<<(ostream &os, const tuple<T1, T2, T3> &t) {
  os << "(" << get<0>(t) << ", " << get<1>(t) << ", " << get<2>(t) << ")";
  return os;
}

template <typename T1, typename T2, typename T3, typename T4>
ostream &operator<<(ostream &os, const tuple<T1, T2, T3, T4> &t) {
  os << "(" << get<0>(t) << ", " << get<1>(t) << ", " << get<2>(t) << ", "
     << get<3>(t) << ")";
  return os;
}

template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  os << '[';
  for (auto it = v.begin(); it != v.end(); it++) {
    if (it != v.begin())
      os << ", ";
    os << *it;
  }
  os << ']';

  return os;
}

template <typename T> ostream &operator<<(ostream &os, const set<T> &v) {
  os << '{';
  for (auto it = v.begin(); it != v.end(); it++) {
    if (it != v.begin())
      os << ", ";
    os << *it;
  }
  os << '}';

  return os;
}

template <typename T> ostream &operator<<(ostream &os, const multiset<T> &v) {
  os << '{';
  for (auto it = v.begin(); it != v.end(); it++) {
    if (it != v.begin())
      os << ", ";
    os << *it;
  }
  os << '}';

  return os;
}

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const map<T1, T2> &mp) {
  os << '[';
  for (auto it = mp.begin(); it != mp.end(); it++) {
    if (it != mp.begin())
      os << ", ";
    os << it->first << ": " << it->second;
  }
  os << ']';

  return os;
}

template <typename T, typename T2, typename T3>
ostream &operator<<(ostream &os, const priority_queue<T, T2, T3> &orig) {
  priority_queue<T, T2, T3> pq(orig);
  bool first = true;
  os << '[';
  while (!pq.empty()) {
    T x = pq.top();
    pq.pop();
    if (!first)
      os << ", ";
    os << x;
    first = false;
  }
  return os << ']';
}

template <typename T> ostream &operator<<(ostream &os, const stack<T> &st) {
  stack<T> tmp(st);
  os << '[';
  bool first = true;
  while (!tmp.empty()) {
    T &t = tmp.top();
    if (first)
      first = false;
    else
      os << ", ";
    os << t;
    tmp.pop();
  }
  os << ']';
  return os;
}

#if __cplusplus >= 201703L
template <typename T> ostream &operator<<(ostream &os, const optional<T> &t) {
  if (t.has_value())
    os << "v(" << t.value() << ")";
  else
    os << "nullopt";
  return os;
}
#endif

// ---- end <<
// ---- inserted library file debug.cc
template <class... Args> string dbgFormat(const char *fmt, Args... args) {
  size_t len = snprintf(nullptr, 0, fmt, args...);
  char buf[len + 1];
  snprintf(buf, len + 1, fmt, args...);
  return string(buf);
}

template <class Head> void dbgLog(Head &&head) { cerr << head << endl; }

template <class Head, class... Tail> void dbgLog(Head &&head, Tail &&...tail) {
  cerr << head << " ";
  dbgLog(forward<Tail>(tail)...);
}

#if DEBUG
#define DLOG(...) dbgLog(__VA_ARGS__)
#define DFMT(...) cerr << dbgFormat(__VA_ARGS__) << endl
#define DCALL(func, ...) func(__VA_ARGS__)
#else
#define DLOG(...)
#define DFMT(...)
#define DCALL(func, ...)
#endif

// ---- end debug.cc
// @@ !! LIM  -- end mark --

int main(int argc, char *argv[]) {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << setprecision(20);

  ll N, K;
  cin >> N >> K;
  vector<ll> A(N);
  for (ll i = 0; i < N; i++)
    cin >> A.at(i);

  auto allN = [&]() -> bool {
    for (ll i = 0; i < N; i++)
      if (A.at(i) < N)
        return false;
    return true;
  };

  for (ll k = 0; k < K; k++) {
    vector<ll> d(N + 1);
    for (ll i = 0; i < N; i++) {
      ll x = max(0LL, i - A.at(i));
      ll y = min(N, i + 1 + A.at(i));
      d.at(x)++;
      d.at(y)--;
    }
    ll sum = 0;
    for (ll i = 0; i < N; i++) {
      sum += d.at(i);
      A.at(i) = sum;
    }
    DLOG("k=", k, "A=", A);
    if (allN())
      break;
  }

  for (ll i = 0; i < N; i++) {
    if (i > 0)
      cout << " ";
    cout << A.at(i);
  }
  cout << endl;

  return 0;
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>
#include <cassert>
typedef long long int ll;
using namespace std;

// @@ !! LIM(debug)
// --> f:<< debug
// ---- inserted function << from util.cc
template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << "(" << p.first << ", " << p.second << ")";
  return os;
}

template <typename T1, typename T2, typename T3>
ostream &operator<<(ostream &os, const tuple<T1, T2, T3> &t) {
  os << "(" << get<0>(t) << ", " << get<1>(t) << ", " << get<2>(t) << ")";
  return os;
}

template <typename T1, typename T2, typename T3, typename T4>
ostream &operator<<(ostream &os, const tuple<T1, T2, T3, T4> &t) {
  os << "(" << get<0>(t) << ", " << get<1>(t) << ", " << get<2>(t) << ", "
     << get<3>(t) << ")";
  return os;
}

template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  os << '[';
  for (auto it = v.begin(); it != v.end(); it++) {
    if (it != v.begin())
      os << ", ";
    os << *it;
  }
  os << ']';

  return os;
}

template <typename T> ostream &operator<<(ostream &os, const set<T> &v) {
  os << '{';
  for (auto it = v.begin(); it != v.end(); it++) {
    if (it != v.begin())
      os << ", ";
    os << *it;
  }
  os << '}';

  return os;
}

template <typename T> ostream &operator<<(ostream &os, const multiset<T> &v) {
  os << '{';
  for (auto it = v.begin(); it != v.end(); it++) {
    if (it != v.begin())
      os << ", ";
    os << *it;
  }
  os << '}';

  return os;
}

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const map<T1, T2> &mp) {
  os << '[';
  for (auto it = mp.begin(); it != mp.end(); it++) {
    if (it != mp.begin())
      os << ", ";
    os << it->first << ": " << it->second;
  }
  os << ']';

  return os;
}

template <typename T, typename T2, typename T3>
ostream &operator<<(ostream &os, const priority_queue<T, T2, T3> &orig) {
  priority_queue<T, T2, T3> pq(orig);
  bool first = true;
  os << '[';
  while (!pq.empty()) {
    T x = pq.top();
    pq.pop();
    if (!first)
      os << ", ";
    os << x;
    first = false;
  }
  return os << ']';
}

template <typename T> ostream &operator<<(ostream &os, const stack<T> &st) {
  stack<T> tmp(st);
  os << '[';
  bool first = true;
  while (!tmp.empty()) {
    T &t = tmp.top();
    if (first)
      first = false;
    else
      os << ", ";
    os << t;
    tmp.pop();
  }
  os << ']';
  return os;
}

#if __cplusplus >= 201703L
template <typename T> ostream &operator<<(ostream &os, const optional<T> &t) {
  if (t.has_value())
    os << "v(" << t.value() << ")";
  else
    os << "nullopt";
  return os;
}
#endif

// ---- end <<
// ---- inserted library file debug.cc
template <class... Args> string dbgFormat(const char *fmt, Args... args) {
  size_t len = snprintf(nullptr, 0, fmt, args...);
  char buf[len + 1];
  snprintf(buf, len + 1, fmt, args...);
  return string(buf);
}

template <class Head> void dbgLog(Head &&head) { cerr << head << endl; }

template <class Head, class... Tail> void dbgLog(Head &&head, Tail &&...tail) {
  cerr << head << " ";
  dbgLog(forward<Tail>(tail)...);
}

#if DEBUG
#define DLOG(...) dbgLog(__VA_ARGS__)
#define DFMT(...) cerr << dbgFormat(__VA_ARGS__) << endl
#define DCALL(func, ...) func(__VA_ARGS__)
#else
#define DLOG(...)
#define DFMT(...)
#define DCALL(func, ...)
#endif

// ---- end debug.cc
// @@ !! LIM  -- end mark --

int main(int argc, char *argv[]) {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << setprecision(20);

  ll N, K;
  cin >> N >> K;
  vector<ll> A(N);
  for (ll i = 0; i < N; i++)
    cin >> A.at(i);

  ll p = -1;
  ll q = -1;
  for (ll k = 0; k < K; k++) {
    vector<ll> d(N + 1);
    {
      ll i = 0;
      while (i < N) {
        if (i == p) {
          d.at(0) += q - p;
          d.at(N) -= q - p;
          i = q;
        } else {
          ll x = max(0LL, i - A.at(i));
          ll y = min(N, i + 1 + A.at(i));
          d.at(x)++;
          d.at(y)--;
          i++;
        }
      }
    }
    ll sum = 0;
    bool incr = true;
    {
      ll i = 0;
      while (i < N) {
        if (i == p) {
          i = q;
        } else {
          sum += d.at(i);
          if (A.at(i) >= sum)
            incr = false;
          A.at(i) = sum;
          i++;
        }
      }
    }
    if (incr && p == -1) {
      ll i = 0;
      while (i < N && A.at(i) < N)
        i++;
      if (i < N) {
        p = i;
        while (i < N && A.at(i) == N)
          i++;
        q = i;
      }
    } else if (p >= 0) {
      while (p - 1 >= 0 && A.at(p - 1) == N)
        p--;
      while (q < N && A.at(q) == N)
        q++;
    }
    DLOG("k=", k, "A=", A, "p=", p, "q=", q);
    if (p == 0 && q == N)
      break;
  }

  for (ll i = 0; i < N; i++) {
    if (i > 0)
      cout << " ";
    if (p <= i && i < q)
      cout << N;
    else
      cout << A.at(i);
  }
  cout << endl;

  return 0;
}