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

#include <algorithm>
#include <bitset>
#include <complex>
#include <cstdint>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits.h>
#include <limits>
#include <list>
#include <map>
#include <math.h>
#include <queue>
#include <regex>
#include <set>
#include <stack>
#include <stdio.h>
#include <string>
#include <time.h>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using pii = pair<int, int>;
using ll = long long;
using ld = long double;
#define pb push_back
#define mp make_pair
#define sc second
#define fr first
#define stpr setprecision
#define cYES cout << "YES" << endl
#define cNO cout << "NO" << endl
#define cYes cout << "Yes" << endl
#define cNo cout << "No" << endl
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define Rep(i, a, b) for (ll i = (a); i < (b); ++i)
#define rrep(i, n) for (ll i = n - 1; i >= 0; i--)
#define rRep(i, a, b) for (ll i = a; i >= b; i--)
#define crep(i) for (char i = 'a'; i <= 'z'; ++i)
#define psortsecond(A, N)                                                      \\
  sort(A, A + N,                                                               \\
       [](const pii &a, const pii &b) { return a.second < b.second; });
#define ALL(x) (x).begin(), (x).end()
#define debug(v)                                                               \\
  cout << #v << ":";                                                           \\
  for (auto x : v) {                                                           \\
    cout << x << ' ';                                                          \\
  }                                                                            \\
  cout << endl;
#define endl '\\n'
int ctoi(const char c) {
  if ('0' <= c && c <= '9')
    return (c - '0');
  return -1;
}
ll gcd(ll a, ll b) { return (b == 0 ? a : gcd(b, a % b)); }
ll lcm(ll a, ll b) { return a * b / gcd(a, b); }
constexpr ll MOD = 1000000007;
constexpr ll INF = 1000000011;
constexpr ll MOD2 = 998244353;
constexpr ll LINF = 1001002003004005006ll;
constexpr ld EPS = 10e-8;
template <class T, class U> inline bool chmax(T &lhs, const U &rhs) {
  if (lhs < rhs) {
    lhs = rhs;
    return 1;
  }
  return 0;
}
template <class T, class U> inline bool chmin(T &lhs, const U &rhs) {
  if (lhs > rhs) {
    lhs = rhs;
    return 1;
  }
  return 0;
}
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &&x : v)
    is >> x;
  return is;
}
template <typename T, typename U>
istream &operator>>(istream &is, pair<T, U> &p) {
  is >> p.first;
  is >> p.second;
  return is;
}
template <typename T, typename U>
ostream &operator>>(ostream &os, const pair<T, U> &p) {
  os << p.first << ' ' << p.second;
  return os;
}
template <class T> ostream &operator<<(ostream &os, vector<T> &v) {
  for (auto i = begin(v); i != end(v); ++i) {
    if (i != begin(v))
      os << ' ';
    os << *i;
  }
  return os;
}

template <std::uint_fast64_t Modulus> class modint {
  using u64 = std::uint_fast64_t;

public:
  u64 a;

  constexpr modint(const u64 x = 0) noexcept : a(x % Modulus) {}
  constexpr u64 &value() noexcept { return a; }
  constexpr const u64 &value() const noexcept { return a; }
  constexpr modint operator+(const modint rhs) const noexcept {
    return modint(*this) += rhs;
  }
  constexpr modint operator-(const modint rhs) const noexcept {
    return modint(*this) -= rhs;
  }
  constexpr modint operator*(const modint rhs) const noexcept {
    return modint(*this) *= rhs;
  }
  constexpr modint operator/(const modint rhs) const noexcept {
    return modint(*this) /= rhs;
  }
  constexpr modint &operator+=(const modint rhs) noexcept {
    a += rhs.a;
    if (a >= Modulus) {
      a -= Modulus;
    }
    return *this;
  }
  constexpr modint &operator-=(const modint rhs) noexcept {
    if (a < rhs.a) {
      a += Modulus;
    }
    a -= rhs.a;
    return *this;
  }
  constexpr modint &operator*=(const modint rhs) noexcept {
    a = a * rhs.a % Modulus;
    return *this;
  }
  constexpr modint &operator/=(modint rhs) noexcept {
    u64 exp = Modulus - 2;
    while (exp) {
      if (exp % 2) {
        *this *= rhs;
      }
      rhs *= rhs;
      exp /= 2;
    }
    return *this;
  }
};
vector<ll> V1, V2;
queue<ll> V3, V4;
modint<MOD> ANS = 1;
ll Z = 0;

int main() {
  ll N, K;
  cin >> N >> K;
  rep(i, N) {
    ll X;
    cin >> X;
    if (X > 0) {
      V1.pb(X);
    } else if (X < 0) {
      V2.pb(abs(X));
    } else {
      Z++;
    }
  }
  sort(ALL(V1));
  reverse(ALL(V1));
  sort(ALL(V2));
  if (V1.size() + V2.size() < K) {
    cout << 0 << endl;
    return 0;
  }
  if ((V1.size() + V2.size() == K && V2.size() % 2 == 1)) {
    if (Z) {
      cout << 0 << endl;
      return 0;
    }
  }
  if (K == V1.size() + V2.size() + Z) {
    rep(i, V1.size()) { ANS *= V1[i]; }
    rep(i, V2.size()) { ANS *= V2[i]; }
    if (V2.size() % 2 == 1) {
      cout << (-ANS.a + MOD) % MOD << endl;
      return 0;
    } else {
      cout << ANS.a << endl;
    }
    return 0;
  }
  if (V1.size() == 0) {
    if (K % 2 == 1) {
      if (Z) {
        cout << 0 << endl;
        return 0;
      }
      rep(i, K) { ANS *= V2[i]; }
      cout << (-ANS.a + MOD) % MOD << endl;
      return 0;
    }
  }
  reverse(ALL(V2));
  for (ll i = 0; i + 1 < V1.size(); i += 2) {
    ll X = 1;
    X *= V1[i];
    X *= V1[i + 1];
    V3.push(X);
  }
  for (ll i = 0; i + 1 < V2.size(); i += 2) {
    ll X = 1;
    X *= V2[i];
    X *= V2[i + 1];
    V4.push(X);
  }
  ll X = K / 2;
  ll P = 0, Q = 0;
  rep(i, X) {
    ll A = V3.front(), B = V4.front();
    // cout << A << " " << B <<  endl;
    if (A > B) {
      ANS *= A % MOD;
      V3.pop();
      P++;
    } else {
      ANS *= B % MOD;
      V4.pop();
    }
  }
  if (K % 2 == 1) {
    if (P * 2 < V1.size()) {
      ANS *= V1[P * 2];
      cout << ANS.a << endl;
      return 0;
    } else {
      ANS = 1;
      rep(i, V1.size() - 1) {
        ANS *= V1[i];
        K--;
      }
      rep(j, K / 2) { ANS *= (V2[2 * j] * V2[2 * j + 1] % MOD); }
      cout << ANS.a << endl;
      return 0;
    }
  } else {
    cout << ANS.a << endl;
  }
}


Error: 0

Fixed submission:

#include <algorithm>
#include <bitset>
#include <complex>
#include <cstdint>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits.h>
#include <limits>
#include <list>
#include <map>
#include <math.h>
#include <queue>
#include <regex>
#include <set>
#include <stack>
#include <stdio.h>
#include <string>
#include <time.h>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using pii = pair<int, int>;
using ll = long long;
using ld = long double;
#define pb push_back
#define mp make_pair
#define sc second
#define fr first
#define stpr setprecision
#define cYES cout << "YES" << endl
#define cNO cout << "NO" << endl
#define cYes cout << "Yes" << endl
#define cNo cout << "No" << endl
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define Rep(i, a, b) for (ll i = (a); i < (b); ++i)
#define rrep(i, n) for (ll i = n - 1; i >= 0; i--)
#define rRep(i, a, b) for (ll i = a; i >= b; i--)
#define crep(i) for (char i = 'a'; i <= 'z'; ++i)
#define psortsecond(A, N)                                                      \\
  sort(A, A + N,                                                               \\
       [](const pii &a, const pii &b) { return a.second < b.second; });
#define ALL(x) (x).begin(), (x).end()
#define debug(v)                                                               \\
  cout << #v << ":";                                                           \\
  for (auto x : v) {                                                           \\
    cout << x << ' ';                                                          \\
  }                                                                            \\
  cout << endl;
#define endl '\\n'
int ctoi(const char c) {
  if ('0' <= c && c <= '9')
    return (c - '0');
  return -1;
}
ll gcd(ll a, ll b) { return (b == 0 ? a : gcd(b, a % b)); }
ll lcm(ll a, ll b) { return a * b / gcd(a, b); }
constexpr ll MOD = 1000000007;
constexpr ll INF = 1000000011;
constexpr ll MOD2 = 998244353;
constexpr ll LINF = 1001002003004005006ll;
constexpr ld EPS = 10e-8;
template <class T, class U> inline bool chmax(T &lhs, const U &rhs) {
  if (lhs < rhs) {
    lhs = rhs;
    return 1;
  }
  return 0;
}
template <class T, class U> inline bool chmin(T &lhs, const U &rhs) {
  if (lhs > rhs) {
    lhs = rhs;
    return 1;
  }
  return 0;
}
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &&x : v)
    is >> x;
  return is;
}
template <typename T, typename U>
istream &operator>>(istream &is, pair<T, U> &p) {
  is >> p.first;
  is >> p.second;
  return is;
}
template <typename T, typename U>
ostream &operator>>(ostream &os, const pair<T, U> &p) {
  os << p.first << ' ' << p.second;
  return os;
}
template <class T> ostream &operator<<(ostream &os, vector<T> &v) {
  for (auto i = begin(v); i != end(v); ++i) {
    if (i != begin(v))
      os << ' ';
    os << *i;
  }
  return os;
}

template <std::uint_fast64_t Modulus> class modint {
  using u64 = std::uint_fast64_t;

public:
  u64 a;

  constexpr modint(const u64 x = 0) noexcept : a(x % Modulus) {}
  constexpr u64 &value() noexcept { return a; }
  constexpr const u64 &value() const noexcept { return a; }
  constexpr modint operator+(const modint rhs) const noexcept {
    return modint(*this) += rhs;
  }
  constexpr modint operator-(const modint rhs) const noexcept {
    return modint(*this) -= rhs;
  }
  constexpr modint operator*(const modint rhs) const noexcept {
    return modint(*this) *= rhs;
  }
  constexpr modint operator/(const modint rhs) const noexcept {
    return modint(*this) /= rhs;
  }
  constexpr modint &operator+=(const modint rhs) noexcept {
    a += rhs.a;
    if (a >= Modulus) {
      a -= Modulus;
    }
    return *this;
  }
  constexpr modint &operator-=(const modint rhs) noexcept {
    if (a < rhs.a) {
      a += Modulus;
    }
    a -= rhs.a;
    return *this;
  }
  constexpr modint &operator*=(const modint rhs) noexcept {
    a = a * rhs.a % Modulus;
    return *this;
  }
  constexpr modint &operator/=(modint rhs) noexcept {
    u64 exp = Modulus - 2;
    while (exp) {
      if (exp % 2) {
        *this *= rhs;
      }
      rhs *= rhs;
      exp /= 2;
    }
    return *this;
  }
};
vector<ll> V1, V2;
queue<ll> V3, V4;
modint<MOD> ANS = 1;
ll Z = 0;

int main() {
  ll N, K;
  cin >> N >> K;
  rep(i, N) {
    ll X;
    cin >> X;
    if (X > 0) {
      V1.pb(X);
    } else if (X < 0) {
      V2.pb(abs(X));
    } else {
      Z++;
    }
  }
  sort(ALL(V1));
  reverse(ALL(V1));
  sort(ALL(V2));
  if (V1.size() + V2.size() < K) {
    cout << 0 << endl;
    return 0;
  }
  if ((V1.size() + V2.size() == K && V2.size() % 2 == 1)) {
    if (Z) {
      cout << 0 << endl;
      return 0;
    }
  }
  if (K == V1.size() + V2.size() && Z == 0) {
    rep(i, V1.size()) { ANS *= V1[i]; }
    rep(i, V2.size()) { ANS *= V2[i]; }
    if (V2.size() % 2 == 1) {
      cout << (-ANS.a + MOD) % MOD << endl;
      return 0;
    } else {
      cout << ANS.a << endl;
    }
    return 0;
  }
  if (V1.size() == 0) {
    if (K % 2 == 1) {
      if (Z) {
        cout << 0 << endl;
        return 0;
      }
      rep(i, K) { ANS *= V2[i]; }
      cout << (-ANS.a + MOD) % MOD << endl;
      return 0;
    } else {
      rep(i, K) { ANS *= V2[i]; }
      cout << ANS.a << endl;
    }
  }
  reverse(ALL(V2));
  for (ll i = 0; i + 1 < V1.size(); i += 2) {
    ll X = 1;
    X *= V2[i];
    X *= V2[i + 1];
    V3.push(X);
  }
  for (ll i = 0; i + 1 < V2.size(); i += 2) {
    ll X = 1;
    X *= V2[i];
    X *= V2[i + 1];
    V4.push(X);
  }
  ll X = K / 2;
  ll P = 0, Q = 0;
  rep(i, X) {
    ll A, B;
    if (V3.size()) {
      A = V3.front();
    } else {
      A = 0;
    }
    if (V3.size()) {
      B = V4.front();
    } else {
      B = 0;
    }
    if (A > B) {
      ANS *= A % MOD;
      V3.pop();
      P++;
    } else {
      ANS *= B % MOD;
      V4.pop();
    }
  }
  if (K % 2 == 1) {
    if (P * 2 < V1.size()) {
      ANS *= V1[P * 2];
      cout << ANS.a << endl;
      return 0;
    } else {
      ANS = 1;
      rep(i, V1.size() - 1) {
        ANS *= V1[i];
        K--;
      }
      rep(j, K / 2) { ANS *= (V2[2 * j] * V2[2 * j + 1] % MOD); }
      cout << ANS.a << endl;
      return 0;
    }
  } else {
    cout << ANS.a << endl;
  }
}