Problem p02869 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <cassert>
#include <chrono>
#include <cmath>
#include <cstdio>
#include <ctime>
#include <functional>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <string>
#include <tuple>
#include <utility>
#include <vector>
using namespace std;

namespace {
using Integer = long long; //__int128;
template <class T, class S> istream &operator>>(istream &is, pair<T, S> &p) {
  return is >> p.first >> p.second;
}
template <class T> istream &operator>>(istream &is, vector<T> &vec) {
  for (T &val : vec)
    is >> val;
  return is;
}
template <class T> istream &operator,(istream &is, T &val) { return is >> val; }
template <class T, class S>
ostream &operator<<(ostream &os, const pair<T, S> &p) {
  return os << p.first << " " << p.second;
}
template <class T> ostream &operator<<(ostream &os, const vector<T> &vec) {
  for (size_t i = 0; i < vec.size(); i++)
    os << vec[i] << (i == vec.size() - 1 ? "" : " ");
  return os;
}
template <class T> ostream &operator,(ostream &os, const T &val) {
  return os << " " << val;
}

// C++14
//  tuple_util::apply( function, result, tuple<args>)
#include <tuple>
#include <utility>
namespace tuple_util {
template <class F, class R, class... Args, size_t... I>
void apply(F &f, R &res, tuple<Args...> &t, index_sequence<I...>) {
  res = f(get<I>(t)...);
}
template <class F, class R, class... Args>
void apply(F &f, R &res, tuple<Args...> &t) {
  apply(f, res, t, index_sequence_for<Args...>{});
}
template <class T, size_t... I>
void input(istream &is, T &t, index_sequence<I...>) {
  using s = int[];
  (void)s{(void(is >> get<I>(t)), 0)...};
}
template <class T, size_t... I>
void output(ostream &os, T &t, index_sequence<I...>) {
  using s = int[];
  (void)s{(void(os << get<I>(t) << " "), 0)...};
}
} // namespace tuple_util
template <class... Args> istream &operator>>(istream &is, tuple<Args...> &t) {
  tuple_util::input(is, t, index_sequence_for<Args...>{});
  return is;
}
template <class... Args>
ostream &operator<<(ostream &os, const tuple<Args...> &t) {
  tuple_util::output(os, t, index_sequence_for<Args...>{});
  return os;
}

template <class H> void print(const H &head) { cout << head; }
template <class H, class... T> void print(const H &head, const T &...tail) {
  cout << head << " ";
  print(tail...);
}
template <class... T> void println(const T &...values) {
  print(values...);
  cout << endl;
}

template <class H> void eprint(const H &head) { cerr << head; }
template <class H, class... T> void eprint(const H &head, const T &...tail) {
  cerr << head << " ";
  eprint(tail...);
}
template <class... T> void eprintln(const T &...values) {
  eprint(values...);
  cerr << endl;
}

class range {
  Integer start_, end_, step_;

public:
  struct range_iterator {
    Integer val, step_;
    range_iterator(Integer v, Integer step) : val(v), step_(step) {}
    Integer operator*() { return val; }
    void operator++() { val += step_; }
    bool operator!=(range_iterator &x) {
      return step_ > 0 ? val < x.val : val > x.val;
    }
  };
  range(Integer len) : start_(0), end_(len), step_(1) {}
  range(Integer start, Integer end) : start_(start), end_(end), step_(1) {}
  range(Integer start, Integer end, Integer step)
      : start_(start), end_(end), step_(step) {}
  range_iterator begin() { return range_iterator(start_, step_); }
  range_iterator end() { return range_iterator(end_, step_); }
};

inline string operator"" _s(const char *str, size_t size) {
  return move(string(str));
}
constexpr Integer my_pow(Integer x, Integer k, Integer z = 1) {
  return k == 0    ? z
         : k == 1  ? z * x
         : (k & 1) ? my_pow(x * x, k >> 1, z * x)
                   : my_pow(x * x, k >> 1, z);
}
constexpr Integer my_pow_mod(Integer x, Integer k, Integer M, Integer z = 1) {
  return k == 0    ? z % M
         : k == 1  ? z * x % M
         : (k & 1) ? my_pow_mod(x * x % M, k >> 1, M, z * x % M)
                   : my_pow_mod(x * x % M, k >> 1, M, z);
}
constexpr unsigned long long operator"" _ten(unsigned long long value) {
  return my_pow(10, value);
}

inline int k_bit(Integer x, int k) { return (x >> k) & 1; } // 0-indexed

mt19937 mt(chrono::duration_cast<chrono::nanoseconds>(
               chrono::steady_clock::now().time_since_epoch())
               .count());

template <class T> string join(const vector<T> &v, const string &sep) {
  stringstream ss;
  for (size_t i = 0; i < v.size(); i++) {
    if (i > 0)
      ss << sep;
    ss << v[i];
  }
  return ss.str();
}

inline string operator*(string s, int k) {
  string ret;
  while (k) {
    if (k & 1)
      ret += s;
    s += s;
    k >>= 1;
  }
  return ret;
}
} // namespace
constexpr long long mod = 9_ten + 7;

int main() {
  long long n, k;
  cin >> n, k;

  if (2 * k - 1 > n) {
    println(-1);
    return 0;
  }

  vector<int> a(n);
  for (int i = 0; i < n; i++) {
    a[i] = 2 * n + i - k;
  }

  vector<int> used(2 * n, 0);
  vector<tuple<int, int, int>> b;
  for (int i = 0, j = n * 2 - 1; i < 2 * n; i += 2, j--) {
    if (i >= j)
      break;
    used[i] = 1;
    used[j] = 1;
    b.emplace_back(i + j, i, j);
  }
  for (int i = 0, j = 2 * n - 1; i < 2 * n; i++, j--) {
    while (i < 2 * n - 1 && used[i])
      i++;
    while (j > i && used[j])
      j--;
    if (i < 2 * n - 1 && j > i) {
      used[i] = 1;
      used[j] = 1;
      b.emplace_back(i + j, i, j);
    }
  }

  sort(b.begin(), b.end());
  assert(b.size() == n);
  for (int i = 0; i < n; i++) {
    int x, y, z;
    tie(ignore, x, y) = b[i];
    z = a[i];
    if (x + y > z) {
      assert(x + y <= z);
    }

    b[i] = make_tuple(x + k, y + k, z + 2 * k);
  }

  println(join(b, "\n"));

  return 0;
}


Fixed submission:
#include <algorithm>
#include <cassert>
#include <chrono>
#include <cmath>
#include <cstdio>
#include <ctime>
#include <functional>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <string>
#include <tuple>
#include <utility>
#include <vector>
using namespace std;

namespace {
using Integer = long long; //__int128;
template <class T, class S> istream &operator>>(istream &is, pair<T, S> &p) {
  return is >> p.first >> p.second;
}
template <class T> istream &operator>>(istream &is, vector<T> &vec) {
  for (T &val : vec)
    is >> val;
  return is;
}
template <class T> istream &operator,(istream &is, T &val) { return is >> val; }
template <class T, class S>
ostream &operator<<(ostream &os, const pair<T, S> &p) {
  return os << p.first << " " << p.second;
}
template <class T> ostream &operator<<(ostream &os, const vector<T> &vec) {
  for (size_t i = 0; i < vec.size(); i++)
    os << vec[i] << (i == vec.size() - 1 ? "" : " ");
  return os;
}
template <class T> ostream &operator,(ostream &os, const T &val) {
  return os << " " << val;
}

// C++14
//  tuple_util::apply( function, result, tuple<args>)
#include <tuple>
#include <utility>
namespace tuple_util {
template <class F, class R, class... Args, size_t... I>
void apply(F &f, R &res, tuple<Args...> &t, index_sequence<I...>) {
  res = f(get<I>(t)...);
}
template <class F, class R, class... Args>
void apply(F &f, R &res, tuple<Args...> &t) {
  apply(f, res, t, index_sequence_for<Args...>{});
}
template <class T, size_t... I>
void input(istream &is, T &t, index_sequence<I...>) {
  using s = int[];
  (void)s{(void(is >> get<I>(t)), 0)...};
}
template <class T, size_t... I>
void output(ostream &os, T &t, index_sequence<I...>) {
  using s = int[];
  (void)s{(void(os << get<I>(t) << " "), 0)...};
}
} // namespace tuple_util
template <class... Args> istream &operator>>(istream &is, tuple<Args...> &t) {
  tuple_util::input(is, t, index_sequence_for<Args...>{});
  return is;
}
template <class... Args>
ostream &operator<<(ostream &os, const tuple<Args...> &t) {
  tuple_util::output(os, t, index_sequence_for<Args...>{});
  return os;
}

template <class H> void print(const H &head) { cout << head; }
template <class H, class... T> void print(const H &head, const T &...tail) {
  cout << head << " ";
  print(tail...);
}
template <class... T> void println(const T &...values) {
  print(values...);
  cout << endl;
}

template <class H> void eprint(const H &head) { cerr << head; }
template <class H, class... T> void eprint(const H &head, const T &...tail) {
  cerr << head << " ";
  eprint(tail...);
}
template <class... T> void eprintln(const T &...values) {
  eprint(values...);
  cerr << endl;
}

class range {
  Integer start_, end_, step_;

public:
  struct range_iterator {
    Integer val, step_;
    range_iterator(Integer v, Integer step) : val(v), step_(step) {}
    Integer operator*() { return val; }
    void operator++() { val += step_; }
    bool operator!=(range_iterator &x) {
      return step_ > 0 ? val < x.val : val > x.val;
    }
  };
  range(Integer len) : start_(0), end_(len), step_(1) {}
  range(Integer start, Integer end) : start_(start), end_(end), step_(1) {}
  range(Integer start, Integer end, Integer step)
      : start_(start), end_(end), step_(step) {}
  range_iterator begin() { return range_iterator(start_, step_); }
  range_iterator end() { return range_iterator(end_, step_); }
};

inline string operator"" _s(const char *str, size_t size) {
  return move(string(str));
}
constexpr Integer my_pow(Integer x, Integer k, Integer z = 1) {
  return k == 0    ? z
         : k == 1  ? z * x
         : (k & 1) ? my_pow(x * x, k >> 1, z * x)
                   : my_pow(x * x, k >> 1, z);
}
constexpr Integer my_pow_mod(Integer x, Integer k, Integer M, Integer z = 1) {
  return k == 0    ? z % M
         : k == 1  ? z * x % M
         : (k & 1) ? my_pow_mod(x * x % M, k >> 1, M, z * x % M)
                   : my_pow_mod(x * x % M, k >> 1, M, z);
}
constexpr unsigned long long operator"" _ten(unsigned long long value) {
  return my_pow(10, value);
}

inline int k_bit(Integer x, int k) { return (x >> k) & 1; } // 0-indexed

mt19937 mt(chrono::duration_cast<chrono::nanoseconds>(
               chrono::steady_clock::now().time_since_epoch())
               .count());

template <class T> string join(const vector<T> &v, const string &sep) {
  stringstream ss;
  for (size_t i = 0; i < v.size(); i++) {
    if (i > 0)
      ss << sep;
    ss << v[i];
  }
  return ss.str();
}

inline string operator*(string s, int k) {
  string ret;
  while (k) {
    if (k & 1)
      ret += s;
    s += s;
    k >>= 1;
  }
  return ret;
}
} // namespace
constexpr long long mod = 9_ten + 7;

int main() {
  long long n, k;
  cin >> n, k;

  if (2 * k - 1 > n) {
    println(-1);
    return 0;
  }

  vector<int> a(n);
  for (int i = 0; i < n; i++) {
    a[i] = 2 * n + i - k;
  }

  vector<int> used(2 * n, 0);
  vector<tuple<int, int, int>> b;
  for (int i = 0, j = n * 2 - 1; i < 2 * n; i += 2, j--) {
    if (i >= j)
      break;
    if (i + j > a.back())
      break;
    used[i] = 1;
    used[j] = 1;
    b.emplace_back(i + j, i, j);
  }
  for (int i = 0, j = 2 * n - 1; i < 2 * n; i++, j--) {
    while (i < 2 * n - 1 && used[i])
      i++;
    while (j > i && used[j])
      j--;
    if (i < 2 * n - 1 && j > i) {
      used[i] = 1;
      used[j] = 1;
      b.emplace_back(i + j, i, j);
    }
  }

  sort(b.begin(), b.end());
  assert(b.size() == n);
  for (int i = 0; i < n; i++) {
    int x, y, z;
    tie(ignore, x, y) = b[i];
    z = a[i];
    if (x + y > z) {
      assert(x + y <= z);
    }

    b[i] = make_tuple(x + k, y + k, z + 2 * k);
  }

  println(join(b, "\n"));

  return 0;
}