Problem p03785 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <vector>

#define len(X) ((int)(X).size())

#ifdef __LOCAL
#define DBG(X) cout << #X << "=" << (X) << '\n';
#else
#define DBG(X)
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

const int INT_INF = (int)(2e9);
const ll LL_INF = (ll)(2e18);

const int NIL = -1;
static mt19937 _g(time(nullptr));

inline ll randint(ll a, ll b) {
  ll w = (_g() << 31LL) ^ _g();
  return a + w % (b - a + 1);
}
inline void fast_io() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
};
template <typename T> inline T sign(T x) { return T(x > 0) - T(x < 0); }
template <typename T, typename S>
inline ostream &operator<<(ostream &os, const pair<T, S> p) {
  cout << "[" << p.first << ";" << p.second << "]";
  return os;
}
template <typename T>
inline ostream &operator<<(ostream &os, const vector<T> &v) {
  for (auto el : v)
    cout << el << " ";
  return os;
}
template <typename T> inline T fetch() {
  T ret;
  cin >> ret;
  return ret;
}
template <typename T> inline vector<T> fetch_vec(int sz) {
  vector<T> ret(sz);
  for (auto &elem : ret)
    cin >> elem;
  return ret;
}

void solve() {
  int n = fetch<int>();
  ll c = fetch<ll>();
  ll k = fetch<ll>();

  auto a = fetch_vec<ll>(n);
  sort(a.begin(), a.end());
  DBG(a);

  ll answ = 0;

  for (int i = 0; i < n;) {
    int j = 0;

    while (j + 1 < n && a[j + 1] - a[i] <= k && (j + 1) - i + 1 <= c) {
      ++j;
    }

    answ += ((ll)(j - i + 1 + c - 1)) / c;
    i = j + 1;
  }

  cout << answ << '\n';
}

int main() {
  fast_io();
  solve();

  return 0;
}


Fixed submission:
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <vector>

#define len(X) ((int)(X).size())

#ifdef __LOCAL
#define DBG(X) cout << #X << "=" << (X) << '\n';
#else
#define DBG(X)
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

const int INT_INF = (int)(2e9);
const ll LL_INF = (ll)(2e18);

const int NIL = -1;
static mt19937 _g(time(nullptr));

inline ll randint(ll a, ll b) {
  ll w = (_g() << 31LL) ^ _g();
  return a + w % (b - a + 1);
}
inline void fast_io() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
};
template <typename T> inline T sign(T x) { return T(x > 0) - T(x < 0); }
template <typename T, typename S>
inline ostream &operator<<(ostream &os, const pair<T, S> p) {
  cout << "[" << p.first << ";" << p.second << "]";
  return os;
}
template <typename T>
inline ostream &operator<<(ostream &os, const vector<T> &v) {
  for (auto el : v)
    cout << el << " ";
  return os;
}
template <typename T> inline T fetch() {
  T ret;
  cin >> ret;
  return ret;
}
template <typename T> inline vector<T> fetch_vec(int sz) {
  vector<T> ret(sz);
  for (auto &elem : ret)
    cin >> elem;
  return ret;
}

void solve() {
  int n = fetch<int>();
  ll c = fetch<ll>();
  ll k = fetch<ll>();

  auto a = fetch_vec<ll>(n);
  sort(a.begin(), a.end());
  DBG(a);

  ll answ = 0;

  for (int i = 0; i < n;) {
    int j = i;

    while (j + 1 < n && a[j + 1] - a[i] <= k && (j + 1) - i + 1 <= c) {
      ++j;
    }

    answ += ((ll)(j - i + 1 + c - 1)) / c;
    i = j + 1;
  }

  cout << answ << '\n';
}

int main() {
  fast_io();
  solve();

  return 0;
}