Problem p03343 (C++)

Buggy submission (status: Time Limit Exceeded):
#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define rep(i, n) for (int i = 0; i < n; ++i)
#define REP(i, n) for (int i = 0; i < n; ++i)
#define range(i, a, b) ((a) <= (i) && (i) < (b))
#define debug(x) cout << #x << ' ' << '=' << ' ' << (x) << endl;
#define fs first
#define sc second
#define pb push_back
#define eb emplace_back
typedef long long ll;
typedef pair<ll, ll> P;
typedef tuple<ll, ll, ll> T;
typedef vector<ll> vec;
typedef vector<P> pvec;
typedef vector<vector<ll>> vvec;
typedef vector<vector<P>> pvvec;
typedef priority_queue<ll> PQI;
typedef priority_queue<P> PQP;
typedef priority_queue<ll, vector<ll>, greater<ll>> PQIG;
typedef priority_queue<P, vector<P>, greater<P>> PQPG;
const vector<int> dx = {0, -1, 0, 1, 1, 1, -1, -1};
const vector<int> dy = {1, 0, -1, 0, 1, -1, 1, -1};
constexpr int MOD = (1000000007);
// const int MOD = (998244353);
// const int INF = (1 << 30); // 1073741824
const int INF = (1LL << 60); // 1152921504606846976
const double EPS = (1 >> 30);
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  is >> p.first >> p.second;
  return is;
}
int nmax = 200000;
vvec g(nmax);

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(15);
  //---------------------------------------------

  int n, k, q;
  cin >> n >> k >> q;
  vector<int> a(n);
  REP(i, n) cin >> a[i];
  int ans = INF;
  for (int mi : a) {
    vec c;
    multiset<int> s;
    for (int i = 0; i <= n; i++) {
      if (i == n || a[i] < mi) {
        sort(all(c));
        rep(j, (int)c.size() - k + 1) { s.insert(c[j]); }
        c.clear();
      } else {
        c.pb(a[i]);
      }
    }
    auto it = s.begin();
    if ((int)s.size() < q)
      continue;
    rep(i, q - 1) it++;
    chmin(ans, *it - mi);
  }
  cout << ans << endl;
}

Fixed submission:
// #define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define rep(i, n) for (int i = 0; i < n; ++i)
#define REP(i, n) for (int i = 0; i < n; ++i)
#define range(i, a, b) ((a) <= (i) && (i) < (b))
#define debug(x) cout << #x << ' ' << '=' << ' ' << (x) << endl;
#define fs first
#define sc second
#define pb push_back
#define eb emplace_back
typedef long long ll;
typedef pair<ll, ll> P;
typedef tuple<ll, ll, ll> T;
typedef vector<ll> vec;
typedef vector<P> pvec;
typedef vector<vector<ll>> vvec;
typedef vector<vector<P>> pvvec;
typedef priority_queue<ll> PQI;
typedef priority_queue<P> PQP;
typedef priority_queue<ll, vector<ll>, greater<ll>> PQIG;
typedef priority_queue<P, vector<P>, greater<P>> PQPG;
const vector<int> dx = {0, -1, 0, 1, 1, 1, -1, -1};
const vector<int> dy = {1, 0, -1, 0, 1, -1, 1, -1};
constexpr int MOD = (1000000007);
// const int MOD = (998244353);
// const int INF = (1 << 30); // 1073741824
const int INF = (1LL << 60); // 1152921504606846976
const double EPS = (1 >> 30);
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  is >> p.first >> p.second;
  return is;
}
int nmax = 200000;
vvec g(nmax);

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(15);
  //---------------------------------------------

  int n, k, q;
  cin >> n >> k >> q;
  vector<int> a(n);
  REP(i, n) cin >> a[i];
  int ans = INF;
  for (int mi : a) {
    vec c;
    multiset<int> s;
    for (int i = 0; i <= n; i++) {
      if (i == n || a[i] < mi) {
        sort(all(c));
        rep(j, (int)c.size() - k + 1) { s.insert(c[j]); }
        c.clear();
      } else {
        c.pb(a[i]);
      }
    }
    auto it = s.begin();
    if ((int)s.size() < q)
      continue;
    rep(i, q - 1) it++;
    chmin(ans, *it - mi);
  }
  cout << ans << endl;
}