Problem p02616 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>

using namespace std;

#define int long long
// #define double long double
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define FORR(i, a, b) for (int i = (a); i > (b); --i)
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define REPR(i, n) for (int i = n; i >= 0; i--)
#define FOREACH(x, a) for (auto &(x) : (a))
#define VECCIN(x)                                                              \\
  for (auto &youso_ : (x))                                                     \\
  cin >> youso_
#define bitcnt(x) __builtin_popcount(x)
#define lbit(x) __builtin_ffsll(x)
#define rbit(x) (64 - __builtin_clzll(x))
#define fi first
#define se second
#define All(a) (a).begin(), (a).end()
#define rAll(a) (a).rbegin(), (a).rend()
#define sz(s) (ll) s.size()
#define cinfast() cin.tie(0), ios::sync_with_stdio(false)
#define debug(x) cerr << #x << " = " << (x) << endl;
#define loop(x)                                                                \\
  LCIN(loop);                                                                  \\
  while (loop--) {                                                             \\
    x;                                                                         \\
  }
#define PERM(c)                                                                \\
  sort(All(c));                                                                \\
  for (bool cp = true; cp; cp = next_permutation(All(c)))
#define COMB(n, k)                                                             \\
  for (ll bit = (1LL << k) - 1; bit < (1LL << n); bit = next_combination(bit))
#define PERM2(n, k)                                                            \\
  COMB(n, k) {                                                                 \\
    vector<int> sel;                                                           \\
    for (int bitindex = 0; bitindex < n; bitindex++)                           \\
      if (bit >> bitindex & 1)                                                 \\
        sel.emplace_back(bitindex);                                            \\
    PERM(sel) { Printv(sel); }                                                 \\
  }
#define MKORDER(n)                                                             \\
  vector<int> od(n);                                                           \\
  iota(All(od), 0LL);

template <typename T = long long> inline T IN() {
  T x;
  cin >> x;
  return (x);
}
inline void CIN() {}
template <class Head, class... Tail>
inline void CIN(Head &&head, Tail &&...tail) {
  cin >> head;
  CIN(move(tail)...);
}
template <class Head> inline void COUT(Head &&head) { cout << (head) << "\\n"; }
template <class Head, class... Tail>
inline void COUT(Head &&head, Tail &&...tail) {
  cout << (head) << " ";
  COUT(forward<Tail>(tail)...);
}

#define CINT(...)                                                              \\
  int __VA_ARGS__;                                                             \\
  CIN(__VA_ARGS__)
#define CCIN(...)                                                              \\
  char __VA_ARGS__;                                                            \\
  CIN(__VA_ARGS__)
#define DCIN(...)                                                              \\
  double __VA_ARGS__;                                                          \\
  CIN(__VA_ARGS__)
#define LCIN(...)                                                              \\
  long long __VA_ARGS__;                                                       \\
  CIN(__VA_ARGS__)
#define SCIN(...)                                                              \\
  string __VA_ARGS__;                                                          \\
  CIN(__VA_ARGS__)
#define Printv(v)                                                              \\
  {                                                                            \\
    REP(hoge, v.size())                                                        \\
    cout << v[hoge] << (hoge == v.size() - 1 ? "" : " ");                      \\
    cout << "\\n";                                                              \\
  }
template <typename T = string> inline void eputs(T s) {
  cout << s << "\\n";
  exit(0);
}
template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
  std::fill((T *)array, (T *)(array + N), val);
}

long long next_combination(long long sub) {
  long long x = sub & -sub, y = sub + x;
  return (((sub & ~y) / x) >> 1) | y;
}
template <class T> inline bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

// generic lambdas
template <typename first>
#if defined(__has_cpp_attribute) && __has_cpp_attribute(nodiscard)
[[nodiscard]]
#elif defined(__GNUC__) &&                                                     \\
    (__GNUC__ > 3 || __GNUC__ == 3 && __GNUC_MINOR__ >= 4)
__attribute__((warn_unused_result))
#endif // defined(__has_cpp_attribute) && __has_cpp_attribute(nodiscard)
static inline constexpr decltype(auto)
fix(first &&f) noexcept {
  return [f = std::forward<first>(f)](auto &&...args) {
    return f(f, std::forward<decltype(args)>(args)...);
  };
}

template <typename T> using PQG = priority_queue<T, vector<T>, greater<T>>;
template <typename T> using PQ = priority_queue<T>;

typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<int, int> PII;
typedef pair<ll, ll> PL;
typedef vector<PL> VPL;
typedef vector<bool> VB;
typedef vector<double> VD;
typedef vector<string> VS;
template <typename T> using V = vector<T>;
template <typename T> using VV = vector<vector<T>>;

const int INF = 1e9;
const ll LINF = 2e18;
const int MOD = 1e9 + 7;
// const int MOD = 998244353;
const int dw[] = {1, 1, 0, -1, -1, -1, 0, 1};
const int dh[] = {0, 1, 1, 1, 0, -1, -1, -1};
#define PI 3.141592653589793230
#define EPS 1e-7

void solve() {
  LCIN(N, K);
  VL as(N);
  VECCIN(as);
  VL pos, neg;
  sort(All(as));
  REP(i, N) {
    if (as[i] >= 0) {
      pos.emplace_back(as[i]);
    } else {
      neg.emplace_back(as[i]);
    }
  }
  ll ans = 1;
  if (sz(neg) == N && K % 2) {
    sort(rAll(neg));
    REP(i, K) {
      ans *= abs(neg[i]);
      ans %= MOD;
    }
    eputs(-ans + MOD);
  }
  if (K == N) {
    REP(i, N) {
      ans *= abs(as[i]);
      ans %= MOD;
    }
    eputs(sz(neg) % 2 ? -ans + MOD : ans);
  }
  ll l = 0, r = N - 1;
  if (K % 2) {
    ans = as[r--];
    K--;
  }
  while (K) {
    if (as[l] * as[l + 1] > as[r] * as[r - 1]) {
      ans *= (as[l] * as[l + 1]) % MOD;
      ans %= MOD;
      l += 2;
    } else {
      ans *= (as[r] * as[r - 1]) % MOD;
      ans %= MOD;
      r -= 2;
    }
    K -= 2;
  }
  COUT(ans);
}

signed main() {
  cinfast();
  // cout << fixed << setprecision(9);
  // loop(solve());
  solve();
}

Error: 0

Fixed submission:

#include <bits/stdc++.h>

using namespace std;

#define int long long
// #define double long double
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define FORR(i, a, b) for (int i = (a); i > (b); --i)
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define REPR(i, n) for (int i = n; i >= 0; i--)
#define FOREACH(x, a) for (auto &(x) : (a))
#define VECCIN(x)                                                              \\
  for (auto &youso_ : (x))                                                     \\
  cin >> youso_
#define bitcnt(x) __builtin_popcount(x)
#define lbit(x) __builtin_ffsll(x)
#define rbit(x) (64 - __builtin_clzll(x))
#define fi first
#define se second
#define All(a) (a).begin(), (a).end()
#define rAll(a) (a).rbegin(), (a).rend()
#define sz(s) (ll) s.size()
#define cinfast() cin.tie(0), ios::sync_with_stdio(false)
#define debug(x) cerr << #x << " = " << (x) << endl;
#define loop(x)                                                                \\
  LCIN(loop);                                                                  \\
  while (loop--) {                                                             \\
    x;                                                                         \\
  }
#define PERM(c)                                                                \\
  sort(All(c));                                                                \\
  for (bool cp = true; cp; cp = next_permutation(All(c)))
#define COMB(n, k)                                                             \\
  for (ll bit = (1LL << k) - 1; bit < (1LL << n); bit = next_combination(bit))
#define PERM2(n, k)                                                            \\
  COMB(n, k) {                                                                 \\
    vector<int> sel;                                                           \\
    for (int bitindex = 0; bitindex < n; bitindex++)                           \\
      if (bit >> bitindex & 1)                                                 \\
        sel.emplace_back(bitindex);                                            \\
    PERM(sel) { Printv(sel); }                                                 \\
  }
#define MKORDER(n)                                                             \\
  vector<int> od(n);                                                           \\
  iota(All(od), 0LL);

template <typename T = long long> inline T IN() {
  T x;
  cin >> x;
  return (x);
}
inline void CIN() {}
template <class Head, class... Tail>
inline void CIN(Head &&head, Tail &&...tail) {
  cin >> head;
  CIN(move(tail)...);
}
template <class Head> inline void COUT(Head &&head) { cout << (head) << "\\n"; }
template <class Head, class... Tail>
inline void COUT(Head &&head, Tail &&...tail) {
  cout << (head) << " ";
  COUT(forward<Tail>(tail)...);
}

#define CINT(...)                                                              \\
  int __VA_ARGS__;                                                             \\
  CIN(__VA_ARGS__)
#define CCIN(...)                                                              \\
  char __VA_ARGS__;                                                            \\
  CIN(__VA_ARGS__)
#define DCIN(...)                                                              \\
  double __VA_ARGS__;                                                          \\
  CIN(__VA_ARGS__)
#define LCIN(...)                                                              \\
  long long __VA_ARGS__;                                                       \\
  CIN(__VA_ARGS__)
#define SCIN(...)                                                              \\
  string __VA_ARGS__;                                                          \\
  CIN(__VA_ARGS__)
#define Printv(v)                                                              \\
  {                                                                            \\
    REP(hoge, v.size())                                                        \\
    cout << v[hoge] << (hoge == v.size() - 1 ? "" : " ");                      \\
    cout << "\\n";                                                              \\
  }
template <typename T = string> inline void eputs(T s) {
  cout << s << "\\n";
  exit(0);
}
template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
  std::fill((T *)array, (T *)(array + N), val);
}

long long next_combination(long long sub) {
  long long x = sub & -sub, y = sub + x;
  return (((sub & ~y) / x) >> 1) | y;
}
template <class T> inline bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

// generic lambdas
template <typename first>
#if defined(__has_cpp_attribute) && __has_cpp_attribute(nodiscard)
[[nodiscard]]
#elif defined(__GNUC__) &&                                                     \\
    (__GNUC__ > 3 || __GNUC__ == 3 && __GNUC_MINOR__ >= 4)
__attribute__((warn_unused_result))
#endif // defined(__has_cpp_attribute) && __has_cpp_attribute(nodiscard)
static inline constexpr decltype(auto)
fix(first &&f) noexcept {
  return [f = std::forward<first>(f)](auto &&...args) {
    return f(f, std::forward<decltype(args)>(args)...);
  };
}

template <typename T> using PQG = priority_queue<T, vector<T>, greater<T>>;
template <typename T> using PQ = priority_queue<T>;

typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<int, int> PII;
typedef pair<ll, ll> PL;
typedef vector<PL> VPL;
typedef vector<bool> VB;
typedef vector<double> VD;
typedef vector<string> VS;
template <typename T> using V = vector<T>;
template <typename T> using VV = vector<vector<T>>;

const int INF = 1e9;
const ll LINF = 2e18;
const int MOD = 1e9 + 7;
// const int MOD = 998244353;
const int dw[] = {1, 1, 0, -1, -1, -1, 0, 1};
const int dh[] = {0, 1, 1, 1, 0, -1, -1, -1};
#define PI 3.141592653589793230
#define EPS 1e-7

void solve() {
  LCIN(N, K);
  VL as(N);
  VECCIN(as);
  VL pos, neg;
  sort(All(as), [&](ll a, ll b) { return abs(a) > abs(b); });
  REP(i, N) {
    if (as[i] >= 0) {
      pos.emplace_back(as[i]);
    } else {
      neg.emplace_back(as[i]);
    }
  }
  if (K == N) {
    ll ans = 1;
    REP(i, N) {
      ans *= abs(as[i]);
      ans %= MOD;
    }
    if (sz(neg) % 2) {
      eputs((-ans + MOD) % MOD);
    } else {
      eputs(ans);
    }
  }
  if (sz(neg) == N && K % 2) {
    sort(rAll(neg));
    ll ans = 1;
    REP(i, K) {
      ans *= abs(neg[i]);
      ans %= MOD;
    }
    eputs((-ans + MOD) % MOD);
  }
  ll ans = 1;
  ll cnt = 0;
  ll pdx = -1, ndx = -1;
  REP(i, K) {
    cnt += as[i] < 0;
    if (as[i] >= 0)
      pdx = i;
    else
      ndx = i;
  }
  if (cnt % 2 == 0) {
    REP(i, K) {
      ans *= abs(as[i]);
      ans %= MOD;
    }
    COUT(ans);
  } else {
    ll pma = 0, nma = 0;
    FOR(i, K, N) {
      if (as[i] >= 0) {
        pma = as[i];
        break;
      }
    }
    FOR(i, K, N) {
      if (as[i] < 0) {
        nma = as[i];
        break;
      }
    }
    if (pdx < 0) {
      assert(~ndx);
      ll ans = 1;
      REP(i, K) {
        if (i == ndx)
          continue;
        ans *= abs(as[i]);
        ans %= MOD;
      }
      ans *= pma;
      COUT(ans);
    } else if (ndx < 0) {
      assert(~pdx);
      ll ans = 1;
      REP(i, K) {
        if (i == pdx)
          continue;
        ans *= abs(as[i]);
        ans %= MOD;
      }
      ans *= nma;
      COUT(ans);
    } else {
      assert(false);
      if (as[pdx] * pma > as[ndx] * nma) {
        ll ans = 1;
        REP(i, K) {
          if (i == ndx)
            continue;
          ans *= abs(as[i]);
          ans %= MOD;
        }
        ans *= pma;
        COUT(ans);
      } else {
        ll ans = 1;
        REP(i, K) {
          if (i == pdx)
            continue;
          ans *= abs(as[i]);
          ans %= MOD;
        }
        ans *= nma;
        COUT(ans);
      }
    }
  }
}

signed main() {
  cinfast();
  // cout << fixed << setprecision(9);
  // loop(solve());
  solve();
}