Problem p02647 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
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;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int N, K;
  cin >> N >> K;
  vector<int> A(N);
  cin >> A;
  vector<int> ans(N), imos(N);
  for (int i = 0; i < N; ++i)
    ans[i] = A[i];
  for (int i = 0; i < K; ++i) {
    for (int j = 0; j < N; ++j)
      imos[j] = 0;
    for (int j = 0; j < N; ++j) {
      ++imos[max(0, j - ans[j])];
      if (j + ans[j] + 1 < N)
        --imos[j + ans[j] + 1];
    }
    for (int j = 0; j < N - 1; ++j)
      imos[j + 1] += imos[j];
    int check = 0;
    for (int j = 0; j < N; ++j) {
      ans[j] = imos[j];
      if (ans[j] != N)
        check = 0;
    }
    if (check)
      break;
  }
  cout << ans << '\n';
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;
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;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int N, K;
  cin >> N >> K;
  vector<int> A(N);
  cin >> A;
  vector<int> ans(N), imos(N);
  for (int i = 0; i < N; ++i)
    ans[i] = A[i];
  for (int i = 0; i < K; ++i) {
    for (int j = 0; j < N; ++j)
      imos[j] = 0;
    for (int j = 0; j < N; ++j) {
      ++imos[max(0, j - ans[j])];
      if (j + ans[j] + 1 < N)
        --imos[j + ans[j] + 1];
    }
    for (int j = 0; j < N - 1; ++j)
      imos[j + 1] += imos[j];
    int check = 1;
    for (int j = 0; j < N; ++j) {
      ans[j] = imos[j];
      if (ans[j] != N)
        check = 0;
    }
    if (check)
      break;
  }
  cout << ans << '\n';
}