Problem p02869 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#include <random>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef double ld;
// #define ll __int128
#define int ll
// #define int ll
// #define char ll
#define double ld
typedef vector<char> vc;
typedef vector<vc> vvc;
typedef vector<vvc> vvvc;
typedef pair<int, int> pii;
typedef pair<pii, pii> piii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<pii> vpi;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<short> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<ld> vld;
typedef vector<vld> vvld;
typedef vector<vvld> vvvld;
typedef vector<string> vst;
typedef vector<vst> vvst;
typedef pair<ld, ld> pld;

#define inmin(a, b) a = min(a, (b))
#define inmax(a, b) a = max(a, (b))
#define ALL(a) a.begin(), a.end()
#define RALL(a) a.rbegin(), a.rend()
#define sqr(x) ((x) * (x))
#define fori(i, n) for (int i = 0; i < int(n); ++i)
#define SZ(a) ((int)((a).size()))
#define triple(T) tuple<T, T, T>
#define quad(T) tuple<T, T, T, T>
#define watch(x) cerr << (#x) << " = " << (x) << endl;

#ifdef MAX_HOME
#define cerr cout
#else
#define cerr                                                                   \
  if (false)                                                                   \
  cerr
#endif

const double PI = 2 * acos(0.0);
#define rand shittttty_shit
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng_64(chrono::steady_clock::now().time_since_epoch().count());

const string DIGITS = "0123456789";
const string ALPH = "abcdefghijklmnopqrstuvwxyz";

template <class T0, class T1>
inline ostream &operator<<(ostream &out, pair<T0, T1> &a) {
  return out << "{" << a.first << ", " << a.second << "}";
}

template <class T0, class T1>
inline istream &operator>>(istream &in, pair<T0, T1> &a) {
  return in >> a.first >> a.second;
}

template <class T0, class T1, class T2>
inline ostream &operator<<(ostream &out, tuple<T0, T1, T2> &a) {
  return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a)
             << "}";
}

template <class T0, class T1, class T2, class T3>
inline ostream &operator<<(ostream &out, tuple<T0, T1, T2, T3> &a) {
  return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a)
             << ", " << get<3>(a) << "}";
}

template <class T> inline ostream &operator<<(ostream &out, vector<T> &a) {
  out << "[";
  fori(i, a.size()) out << a[i]
                        << vector<string>{", ", "]  "}[i + 1 == a.size()];
  return out;
}

void smain();

signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
#ifdef MAX_HOME
  freopen("input.txt", "r", stdin);
  clock_t start = clock();
#endif
  cout << setprecision(12) << fixed;
  smain();
#ifdef MAX_HOME
  cout << "\n\nTOTAL EXECUTION TIME: "
       << float(clock() - start) / CLOCKS_PER_SEC << endl;
#endif
  return 0;
}

bool rec(vi a, vector<pair<int, pii>> &res) {
  if (a.empty())
    return true;
  for (int i = 1; i < a.size(); ++i) {
    for (int j = i + 1; j < a.size(); ++j) {
      if (a[0] + a[i] <= a[j]) {
        vi b = a;
        b.erase(b.begin() + j);
        b.erase(b.begin() + i);
        b.erase(b.begin() + 0);
        if (rec(b, res)) {
          res.push_back({a[0], {a[i], a[j]}});
          return true;
        }
      }
    }
  }
  return false;
}

vector<pair<int, pii>> solve(int k, int n) {
  vi a(3 * n);
  fori(i, 3 * n) { a[i] = k + i; }
  vector<pair<int, pii>> ret;
  rec(a, ret);
  return ret;
}

void bad() {
  cout << "-1";
  exit(0);
}

void smain() {

  int n, k;
  cin >> n >> k;

  vector<pair<int, pii>> aans = solve(k, n);
  watch(aans);

  vi hi;
  fori(i, n) { hi.push_back(2 * n + k + i); }

  vi a(n), b(n);
  fori(i, n) {
    a[i] = k + i;
    b[i] = k + n + i;
  }
  int f = -1;
  for (int i = n - 1; i >= 0; --i) {
    if (b[n - 1] + a[i] <= hi.back()) {
      f = i;
      break;
    }
  }
  if (f == -1) {
    bad();
  }

  vector<pair<int, pii>> kek;

  for (int i = n - 1; i >= 0; --i) {
    kek.push_back({b[i] + a[f], {b[i], a[f]}});
    f--;
    if (f == -1)
      f = n - 1;
  }
  sort(ALL(kek));
  fori(i, n) {
    if (kek[i].first > hi[i])
      bad();
  }

  fori(i, n) {
    cout << kek[i].second.first << ' ' << kek[i].second.second << ' ' << hi[i]
         << '\n';
  }
}

Fixed submission:
#include <bits/stdc++.h>
#include <random>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef double ld;
// #define ll __int128
#define int ll
// #define int ll
// #define char ll
#define double ld
typedef vector<char> vc;
typedef vector<vc> vvc;
typedef vector<vvc> vvvc;
typedef pair<int, int> pii;
typedef pair<pii, pii> piii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<pii> vpi;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<short> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<ld> vld;
typedef vector<vld> vvld;
typedef vector<vvld> vvvld;
typedef vector<string> vst;
typedef vector<vst> vvst;
typedef pair<ld, ld> pld;

#define inmin(a, b) a = min(a, (b))
#define inmax(a, b) a = max(a, (b))
#define ALL(a) a.begin(), a.end()
#define RALL(a) a.rbegin(), a.rend()
#define sqr(x) ((x) * (x))
#define fori(i, n) for (int i = 0; i < int(n); ++i)
#define SZ(a) ((int)((a).size()))
#define triple(T) tuple<T, T, T>
#define quad(T) tuple<T, T, T, T>
#define watch(x) cerr << (#x) << " = " << (x) << endl;

#ifdef MAX_HOME
#define cerr cout
#else
#define cerr                                                                   \
  if (false)                                                                   \
  cerr
#endif

const double PI = 2 * acos(0.0);
#define rand shittttty_shit
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng_64(chrono::steady_clock::now().time_since_epoch().count());

const string DIGITS = "0123456789";
const string ALPH = "abcdefghijklmnopqrstuvwxyz";

template <class T0, class T1>
inline ostream &operator<<(ostream &out, pair<T0, T1> &a) {
  return out << "{" << a.first << ", " << a.second << "}";
}

template <class T0, class T1>
inline istream &operator>>(istream &in, pair<T0, T1> &a) {
  return in >> a.first >> a.second;
}

template <class T0, class T1, class T2>
inline ostream &operator<<(ostream &out, tuple<T0, T1, T2> &a) {
  return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a)
             << "}";
}

template <class T0, class T1, class T2, class T3>
inline ostream &operator<<(ostream &out, tuple<T0, T1, T2, T3> &a) {
  return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a)
             << ", " << get<3>(a) << "}";
}

template <class T> inline ostream &operator<<(ostream &out, vector<T> &a) {
  out << "[";
  fori(i, a.size()) out << a[i]
                        << vector<string>{", ", "]  "}[i + 1 == a.size()];
  return out;
}

void smain();

signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
#ifdef MAX_HOME
  freopen("input.txt", "r", stdin);
  clock_t start = clock();
#endif
  cout << setprecision(12) << fixed;
  smain();
#ifdef MAX_HOME
  cout << "\n\nTOTAL EXECUTION TIME: "
       << float(clock() - start) / CLOCKS_PER_SEC << endl;
#endif
  return 0;
}

bool rec(vi a, vector<pair<int, pii>> &res) {
  if (a.empty())
    return true;
  for (int i = 1; i < a.size(); ++i) {
    for (int j = i + 1; j < a.size(); ++j) {
      if (a[0] + a[i] <= a[j]) {
        vi b = a;
        b.erase(b.begin() + j);
        b.erase(b.begin() + i);
        b.erase(b.begin() + 0);
        if (rec(b, res)) {
          res.push_back({a[0], {a[i], a[j]}});
          return true;
        }
      }
    }
  }
  return false;
}

vector<pair<int, pii>> solve(int k, int n) {
  vi a(3 * n);
  fori(i, 3 * n) { a[i] = k + i; }
  vector<pair<int, pii>> ret;
  rec(a, ret);
  return ret;
}

void bad() {
  cout << "-1";
  exit(0);
}

void smain() {

  int n, k;
  cin >> n >> k;

  //    vector<pair<int, pii>> aans = solve(k, n);
  //    watch(aans);

  vi hi;
  fori(i, n) { hi.push_back(2 * n + k + i); }

  vi a(n), b(n);
  fori(i, n) {
    a[i] = k + i;
    b[i] = k + n + i;
  }
  int f = -1;
  for (int i = n - 1; i >= 0; --i) {
    if (b[n - 1] + a[i] <= hi.back()) {
      f = i;
      break;
    }
  }
  if (f == -1) {
    bad();
  }

  vector<pair<int, pii>> kek;

  for (int i = n - 1; i >= 0; --i) {
    kek.push_back({b[i] + a[f], {b[i], a[f]}});
    f--;
    if (f == -1)
      f = n - 1;
  }
  sort(ALL(kek));
  fori(i, n) {
    if (kek[i].first > hi[i])
      bad();
  }

  fori(i, n) {
    cout << kek[i].second.first << ' ' << kek[i].second.second << ' ' << hi[i]
         << '\n';
  }
}