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

#include <bits/stdc++.h>
using namespace std;

#define int long long
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define reps(i, n) for (int i = 1; i <= (int)(n); i++)
#define all(x) (x).begin(), (x).end()
#define uniq(x) (x).erase(unique(all(x)), (x).end()))
#define bit(n) (1LL << (n))
#define cdiv(a, b) (((a)-1) / (b) + 1)
#define dump(x) cerr << #x " = " << (x) << endl
using vint = vector<int>;
using vvint = vector<vint>;
using pint = pair<int, int>;
using vpint = vector<pint>;
template <typename T>
using priority_queue_rev = priority_queue<T, vector<T>, greater<T>>;
constexpr double PI = 3.1415926535897932384626433832795028;
constexpr int DY[8] = {0, 1, 0, -1, 1, 1, -1, -1};
constexpr int DX[8] = {1, 0, -1, 0, 1, -1, -1, 1};
int gcd(int a, int b) {
  while (b) {
    swap(a %= b, b);
  }
  return a;
}
int lcm(int a, int b) { return a / gcd(a, b) * b; }
template <typename T> void fin(T mes) {
  cout << mes << endl;
  exit(0);
}
template <typename T, typename U> bool chmax(T &a, const U &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T, typename U> bool chmin(T &a, const U &b) {
  if (b < a) {
    a = b;
    return true;
  }
  return false;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &rhs) {
  os << "(" << rhs.first << ", " << rhs.second << ")";
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &rhs) {
  os << "{";
  for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
    os << *itr << (next(itr) != rhs.end() ? ", " : "");
  }
  os << "}";
  return os;
}
struct setup {
  static constexpr int PREC = 20;
  setup() {
    cout << fixed << setprecision(PREC);
    cerr << fixed << setprecision(PREC);
  };
} setup;

template <typename M> struct fenwick_tree {
  using T = typename M::T;
  int n;
  std::vector<T> data;
  fenwick_tree(int n) : n(n), data(n + 1, M::id()) {}
  void add(int i, const T &x) {
    assert(0 <= i && i < n);
    for (i++; i <= n; i += i & -i) {
      data[i] = M::op(data[i], x);
    }
  }
  T get_sum(int i) const {
    assert(0 < i && i <= n);
    T ret = M::id();
    for (; i > 0; i -= i & -i) {
      ret = M::op(ret, data[i]);
    }
    return ret;
  }
  T get_sum(int l, int r) const {
    assert(0 <= l && l < n);
    assert(0 < r && r <= n);
    return M::op(get_sum(r), M::inv(get_sum(l)));
  }
};

template <typename M> struct fenwick_tree_range {
  using T = typename M::T;
  fenwick_tree<M> ft;
  fenwick_tree_range(int n) : ft(n + 1) {}
  void add(int l, int r, const T &x) { ft.add(l, x), ft.add(r, -x); }
  T operator[](int i) const { return ft.get_sum(i + 1); }
};

struct rsq {
  using T = int;
  static T id() { return 0; }
  static T op(const T &a, const T &b) { return a + b; }
  static T inv(const T &a) { return -a; }
};

signed main() {
  int N, K;
  cin >> N >> K;
  vint A(N);
  rep(i, N) { cin >> A[i]; }
  rep(i, min(100LL, K)) {
    fenwick_tree_range<rsq> B(N);
    rep(j, N) { B.add(max(0LL, j - A[j]), min(N, j + A[j] + 1), 1); }
    rep(j, N) { A[j] = B[j]; }
  }
  rep(i, N) { cout << A[i] << endl; }
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;

#define int long long
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define reps(i, n) for (int i = 1; i <= (int)(n); i++)
#define all(x) (x).begin(), (x).end()
#define uniq(x) (x).erase(unique(all(x)), (x).end()))
#define bit(n) (1LL << (n))
#define cdiv(a, b) (((a)-1) / (b) + 1)
#define dump(x) cerr << #x " = " << (x) << endl
using vint = vector<int>;
using vvint = vector<vint>;
using pint = pair<int, int>;
using vpint = vector<pint>;
template <typename T>
using priority_queue_rev = priority_queue<T, vector<T>, greater<T>>;
constexpr double PI = 3.1415926535897932384626433832795028;
constexpr int DY[8] = {0, 1, 0, -1, 1, 1, -1, -1};
constexpr int DX[8] = {1, 0, -1, 0, 1, -1, -1, 1};
int gcd(int a, int b) {
  while (b) {
    swap(a %= b, b);
  }
  return a;
}
int lcm(int a, int b) { return a / gcd(a, b) * b; }
template <typename T> void fin(T mes) {
  cout << mes << endl;
  exit(0);
}
template <typename T, typename U> bool chmax(T &a, const U &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T, typename U> bool chmin(T &a, const U &b) {
  if (b < a) {
    a = b;
    return true;
  }
  return false;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &rhs) {
  os << "(" << rhs.first << ", " << rhs.second << ")";
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &rhs) {
  os << "{";
  for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
    os << *itr << (next(itr) != rhs.end() ? ", " : "");
  }
  os << "}";
  return os;
}
struct setup {
  static constexpr int PREC = 20;
  setup() {
    cout << fixed << setprecision(PREC);
    cerr << fixed << setprecision(PREC);
  };
} setup;

template <typename M> struct fenwick_tree {
  using T = typename M::T;
  int n;
  std::vector<T> data;
  fenwick_tree(int n) : n(n), data(n + 1, M::id()) {}
  void add(int i, const T &x) {
    assert(0 <= i && i < n);
    for (i++; i <= n; i += i & -i) {
      data[i] = M::op(data[i], x);
    }
  }
  T get_sum(int i) const {
    assert(0 < i && i <= n);
    T ret = M::id();
    for (; i > 0; i -= i & -i) {
      ret = M::op(ret, data[i]);
    }
    return ret;
  }
  T get_sum(int l, int r) const {
    assert(0 <= l && l < n);
    assert(0 < r && r <= n);
    return M::op(get_sum(r), M::inv(get_sum(l)));
  }
};

template <typename M> struct fenwick_tree_range {
  using T = typename M::T;
  fenwick_tree<M> ft;
  fenwick_tree_range(int n) : ft(n + 1) {}
  void add(int l, int r, const T &x) { ft.add(l, x), ft.add(r, -x); }
  T operator[](int i) const { return ft.get_sum(i + 1); }
};

struct rsq {
  using T = int;
  static T id() { return 0; }
  static T op(const T &a, const T &b) { return a + b; }
  static T inv(const T &a) { return -a; }
};

signed main() {
  int N, K;
  cin >> N >> K;
  vint A(N);
  rep(i, N) { cin >> A[i]; }
  rep(i, min(1000LL, K)) {
    fenwick_tree_range<rsq> B(N);
    rep(j, N) { B.add(max(0LL, j - A[j]), min(N, j + A[j] + 1), 1); }
    rep(j, N) { A[j] = B[j]; }
  }
  rep(i, N) { cout << A[i] << endl; }
}