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

#include <algorithm>
#include <iostream>
#include <numeric>
#include <string>
#include <tuple>
#include <utility>
#include <vector>

#define REP(i, a, b) for (int i = int(a); i < int(b); i++)
using namespace std;
using ll = long long int;
using P = pair<ll, ll>;

// clang-format off
#ifdef _DEBUG_
#define dump(...) do{ cerr << __LINE__ << ":\\t" << #__VA_ARGS__ << " = "; PPPPP(__VA_ARGS__); cerr << endl; } while(false)
template<typename T> void PPPPP(T t) { cerr << t; }
template<typename T, typename... S> void PPPPP(T t, S... s) { cerr << t << ", "; PPPPP(s...); }
#else
#define dump(...) do{ } while(false)
#endif
template<typename T> vector<T> make_v(size_t a, T b) { return vector<T>(a, b); }
template<typename... Ts> auto make_v(size_t a, Ts... ts) { return vector<decltype(make_v(ts...))>(a, make_v(ts...)); }
template<typename T> bool chmin(T &a, T b) { if (a > b) {a = b; return true; } return false; }
template<typename T> bool chmax(T &a, T b) { if (a < b) {a = b; return true; } return false; }
template<typename T> void print(T a) { cout << a << endl; }
template<typename T, typename... Ts> void print(T a, Ts... ts) { cout << a << ' '; print(ts...); }
template<typename T> istream &operator,(istream &in, T &t) { return in >> t; }
// clang-format on

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int n, k;
  cin, n, k;
  vector<int> a(n);
  REP(i, 0, n) { cin, a[i]; }
  REP(t, 0, k) {
    vector<int> imos(n, 0);
    REP(i, 0, n) {
      int l = max(0, i - a[i]);
      int r = min(n, i + a[i] + 1);
      imos[l]++;
      if (r != n) {
        imos[r]--;
      }
    }
    REP(i, 0, n - 1) { imos[i + 1] += imos[i]; }
    a = move(imos);
    bool ok = true;
    REP(i, 0, n) {
      if (a[i] != n)
        ok = false;
    }
    if (ok) {
      dump(t);
      break;
    }
  }
  REP(i, 0, n) { cout << a[i] << " \\n"[i + 1 == n]; }

  return 0;
}


Error: TLE

Fixed submission:

#include <algorithm>
#include <iostream>
#include <numeric>
#include <string>
#include <tuple>
#include <utility>
#include <vector>

#define REP(i, a, b) for (int i = int(a); i < int(b); i++)
using namespace std;
using ll = long long int;
using P = pair<ll, ll>;

// clang-format off
#ifdef _DEBUG_
#define dump(...) do{ cerr << __LINE__ << ":\\t" << #__VA_ARGS__ << " = "; PPPPP(__VA_ARGS__); cerr << endl; } while(false)
template<typename T> void PPPPP(T t) { cerr << t; }
template<typename T, typename... S> void PPPPP(T t, S... s) { cerr << t << ", "; PPPPP(s...); }
#else
#define dump(...) do{ } while(false)
#endif
template<typename T> vector<T> make_v(size_t a, T b) { return vector<T>(a, b); }
template<typename... Ts> auto make_v(size_t a, Ts... ts) { return vector<decltype(make_v(ts...))>(a, make_v(ts...)); }
template<typename T> bool chmin(T &a, T b) { if (a > b) {a = b; return true; } return false; }
template<typename T> bool chmax(T &a, T b) { if (a < b) {a = b; return true; } return false; }
template<typename T> void print(T a) { cout << a << endl; }
template<typename T, typename... Ts> void print(T a, Ts... ts) { cout << a << ' '; print(ts...); }
template<typename T> istream &operator,(istream &in, T &t) { return in >> t; }
// clang-format on

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int n, k;
  cin, n, k;
  vector<int> a(n);
  REP(i, 0, n) { cin, a[i]; }
  REP(t, 0, k) {
    vector<int> imos(n, 0);
    REP(i, 0, n) {
      int l = max(0, i - a[i]);
      int r = min(n, i + a[i] + 1);
      imos[l]++;
      if (r != n) {
        imos[r]--;
      }
    }
    REP(i, 0, n - 1) { imos[i + 1] += imos[i]; }
    a = move(imos);
  }
  REP(i, 0, n) { cout << a[i] << " \\n"[i + 1 == n]; }

  return 0;
}