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

// clang-format off
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define stoi stoll
using pii = pair<int,int>;
using vi = vector<int>;
using vvi = vector<vi>;
#define all(c) begin(c), end(c)
#define rall(c) rbegin(c), rend(c)
#define fore(x, c) for(auto &&x : c)
#define rep(i, a, n) for(int i = a, i##len = (int)(n); i < i##len; ++i)
#define rrep(i, a, n) for(int i = (int)(n - 1); i >= a; --i)
#define sz(c) ((int)c.size())
#define contains(c, x) (c.find(x) != end(c))
#define inseg(l, x, r) ((l) <= (x) && (x) < (r))
#define dump(...)
#define pb push_back
#define eb emplace_back
#define _ 0
const signed INF_ = 1001001001; const long long INF = 1001001001001001001LL;
const int DX[9] = {0,1,0,-1,1,1,-1,-1,0}, DY[9] = {-1,0,1,0,-1,1,1,-1,0};
template<class T> ostream& operator<<(ostream &os, const vector<T> &v) {
  for (auto i = begin(v); i != end(v); i++) os<<*i<<(i==end(v)-1?"":" ");return os;}
template<class T> istream& operator>>(istream &is, vector<T> &v) {
  for (auto i = begin(v); i != end(v); i++) is>>*i;return is;}
template<class T,class U> istream& operator>>(istream &is, pair<T,U> &p) {
  is>>p.first>>p.second;return is;}
template<class T, class U> bool chmax(T &a, const U &b){return a<b?a=b,1:0;}
template<class T, class U> bool chmin(T &a, const U &b){return a>b?a=b,1:0;}
template <class T> void psum(T& c) {partial_sum(begin(c), end(c), begin(c));}
template<class T> using heap = priority_queue<T, deque<T>, greater<T>>;
struct before_main_function {
  before_main_function() {
      cin.tie(nullptr); ios::sync_with_stdio(false);
      cout << setprecision(15) << fixed;
  }
} before_main_function;
// clang-format on
//------------------8<------------------------------------8<--------------------

template <int mod> class ModInt {
public:
  ModInt() : v(0) {}
  ModInt(int x) : v((x + mod) % mod) {}
  int value() const { return v; }
  const ModInt operator+(const ModInt &r) const {
    return ModInt(this->v + r.v);
  }
  const ModInt operator-(const ModInt &r) const {
    return ModInt(this->v + mod - r.v);
  }
  const ModInt operator*(const ModInt &r) const {
    return ModInt(this->v * r.v);
  }
  const ModInt operator/(const ModInt &r) const { return (*this * (~r)); }
  const ModInt operator^(int k) const { return ModInt(bpow(this->v, k)); }
  const ModInt operator~() const { return ModInt(bpow(this->v, mod - 2)); }
  bool operator==(const ModInt &r) const { return this->v == r.v; }
  bool operator!=(const ModInt &r) const { return this->v != r.v; }
  ModInt &operator+=(const ModInt &r) { return *this = *this + r; }
  ModInt &operator-=(const ModInt &r) { return *this = *this - r; }
  ModInt &operator*=(const ModInt &r) { return *this = *this * r; }
  ModInt &operator/=(const ModInt &r) { return *this = *this * (~r); }

private:
  int v;
  int bpow(int a, int b) const {
    int ret = 1;
    while (b > 0) {
      if (b & 1)
        ret = (ret * a) % mod;
      a = (a * a) % mod;
      b >>= 1;
    }
    return ret;
  }
};
using Mint = ModInt<1000000007>;

signed main() {
  int N, K;
  cin >> N >> K;
  vector<pii> A;
  multiset<int> pos[2], neg[2];
  int zero = 0;
  int neg_cnt = 0;

  rep(i, 0, N) {
    int x;
    cin >> x;
    if (x == 0) {
      zero++;
    } else {
      A.eb(abs(x), x < 0);
      if (x < 0)
        neg_cnt++;
    }
  }
  sort(rall(A));

  if (sz(A) < K) {
    cout << 0 << endl;
    return 0;
  }

  Mint ans = 1;
  int sig = 1;
  rep(i, 0, K) {
    ans *= Mint(A[i].first);
    if (A[i].second) {
      sig *= -1;
      neg[0].insert(A[i].first);
    } else {
      pos[0].insert(A[i].first);
    }
  }
  rep(i, K, sz(A)) {
    if (A[i].second) {
      neg[1].insert(A[i].first);
    } else {
      pos[1].insert(A[i].first);
    }
  }

  if (K == N || (neg_cnt == N && K % 2)) {
    ans = 1;
    rep(i, sz(A) - K, sz(A)) {
      int t = A[i].first;
      if (A[i].second)
        t *= -1;
      ans *= Mint(t);
    }
    cout << ans.value() << endl;
    return 0;
  }

  if (sig > 0) {
    cout << ans.value() << endl;
    return 0;
  }

  Mint ans1 = ans, ans2 = ans;
  int rem1 = -1, add1 = -1;
  int rem2 = -1, add2 = -1;
  bool ans1_valid = false;
  bool ans2_valid = false;

  // remove neg
  if (sz(neg[0])) {
    rem1 = *neg[0].begin();
    ans1 /= Mint(rem1);
  }
  if (rem1 != -1) {
    if (sz(pos[1])) {
      add1 = *pos[1].rbegin();
      ans1 *= Mint(add1);
      ans1_valid = true;
    } else if (zero) {
      ans1 = 0;
      ans1_valid = true;
    }
  }
  // remove pos
  if (sz(pos[0])) {
    rem2 = *pos[0].begin();
    ans2 /= Mint(rem2);
  }
  if (rem2 != -1) {
    if (sz(neg[1])) {
      add2 = *neg[1].rbegin();
      ans2 *= Mint(add2);
      ans2_valid = true;
    } else if (zero) {
      ans2 = 0;
      ans2_valid = true;
    }
  }

  if (ans1_valid && ans2_valid) {
    if (add1 * rem2 >= add2 * rem1) {
      ans = ans1;
    } else {
      ans = ans2;
    }
  } else if (ans1_valid) {
    ans = ans1;
  } else if (ans2_valid) {
    ans = ans2;
  } else if (zero) {
    ans = 0;
  }
  cout << ans.value() << endl;
  return (0 ^ _ ^ 0);
}


Error: 0

Fixed submission:

// clang-format off
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define stoi stoll
using pii = pair<int,int>;
using vi = vector<int>;
using vvi = vector<vi>;
#define all(c) begin(c), end(c)
#define rall(c) rbegin(c), rend(c)
#define fore(x, c) for(auto &&x : c)
#define rep(i, a, n) for(int i = a, i##len = (int)(n); i < i##len; ++i)
#define rrep(i, a, n) for(int i = (int)(n - 1); i >= a; --i)
#define sz(c) ((int)c.size())
#define contains(c, x) (c.find(x) != end(c))
#define inseg(l, x, r) ((l) <= (x) && (x) < (r))
#define dump(...)
#define pb push_back
#define eb emplace_back
#define _ 0
const signed INF_ = 1001001001; const long long INF = 1001001001001001001LL;
const int DX[9] = {0,1,0,-1,1,1,-1,-1,0}, DY[9] = {-1,0,1,0,-1,1,1,-1,0};
template<class T> ostream& operator<<(ostream &os, const vector<T> &v) {
  for (auto i = begin(v); i != end(v); i++) os<<*i<<(i==end(v)-1?"":" ");return os;}
template<class T> istream& operator>>(istream &is, vector<T> &v) {
  for (auto i = begin(v); i != end(v); i++) is>>*i;return is;}
template<class T,class U> istream& operator>>(istream &is, pair<T,U> &p) {
  is>>p.first>>p.second;return is;}
template<class T, class U> bool chmax(T &a, const U &b){return a<b?a=b,1:0;}
template<class T, class U> bool chmin(T &a, const U &b){return a>b?a=b,1:0;}
template <class T> void psum(T& c) {partial_sum(begin(c), end(c), begin(c));}
template<class T> using heap = priority_queue<T, deque<T>, greater<T>>;
struct before_main_function {
  before_main_function() {
      cin.tie(nullptr); ios::sync_with_stdio(false);
      cout << setprecision(15) << fixed;
  }
} before_main_function;
// clang-format on
//------------------8<------------------------------------8<--------------------

template <int mod> class ModInt {
public:
  ModInt() : v(0) {}
  ModInt(int x) : v((x + mod) % mod) {}
  int value() const { return v; }
  const ModInt operator+(const ModInt &r) const {
    return ModInt(this->v + r.v);
  }
  const ModInt operator-(const ModInt &r) const {
    return ModInt(this->v + mod - r.v);
  }
  const ModInt operator*(const ModInt &r) const {
    return ModInt(this->v * r.v);
  }
  const ModInt operator/(const ModInt &r) const { return (*this * (~r)); }
  const ModInt operator^(int k) const { return ModInt(bpow(this->v, k)); }
  const ModInt operator~() const { return ModInt(bpow(this->v, mod - 2)); }
  bool operator==(const ModInt &r) const { return this->v == r.v; }
  bool operator!=(const ModInt &r) const { return this->v != r.v; }
  ModInt &operator+=(const ModInt &r) { return *this = *this + r; }
  ModInt &operator-=(const ModInt &r) { return *this = *this - r; }
  ModInt &operator*=(const ModInt &r) { return *this = *this * r; }
  ModInt &operator/=(const ModInt &r) { return *this = *this * (~r); }

private:
  int v;
  int bpow(int a, int b) const {
    int ret = 1;
    while (b > 0) {
      if (b & 1)
        ret = (ret * a) % mod;
      a = (a * a) % mod;
      b >>= 1;
    }
    return ret;
  }
};
using Mint = ModInt<1000000007>;

signed main() {
  int N, K;
  cin >> N >> K;
  vector<pii> A;
  multiset<int> pos[2], neg[2];
  int zero = 0;
  int neg_cnt = 0;

  rep(i, 0, N) {
    int x;
    cin >> x;
    if (x == 0) {
      zero++;
      continue;
    } else {
      A.eb(abs(x), x < 0);
      if (x < 0)
        neg_cnt++;
    }
  }
  sort(rall(A));

  if (sz(A) < K) {
    cout << 0 << endl;
    return 0;
  }

  Mint ans = 1;
  int sig = 1;
  rep(i, 0, K) {
    ans *= Mint(A[i].first);
    if (A[i].second) {
      sig *= -1;
      neg[0].insert(A[i].first);
    } else {
      pos[0].insert(A[i].first);
    }
  }
  rep(i, K, sz(A)) {
    if (A[i].second) {
      neg[1].insert(A[i].first);
    } else {
      pos[1].insert(A[i].first);
    }
  }

  if (K == N || (neg_cnt == N && K % 2)) {
    ans = 1;
    rep(i, sz(A) - K, sz(A)) {
      int t = A[i].first;
      if (A[i].second)
        t *= -1;
      ans *= Mint(t);
    }
    cout << ans.value() << endl;
    return 0;
  }

  if (sig > 0) {
    cout << ans.value() << endl;
    return 0;
  }

  Mint ans1 = ans, ans2 = ans;
  int rem1 = -1, add1 = -1;
  int rem2 = -1, add2 = -1;
  bool ans1_valid = false;
  bool ans2_valid = false;

  // remove neg
  if (sz(neg[0])) {
    rem1 = *neg[0].begin();
    ans1 /= Mint(rem1);
  }
  if (rem1 != -1) {
    if (sz(pos[1])) {
      add1 = *pos[1].rbegin();
      ans1 *= Mint(add1);
      ans1_valid = true;
    } else if (zero) {
      ans1 = 0;
      ans1_valid = true;
    }
  }
  // remove pos
  if (sz(pos[0])) {
    rem2 = *pos[0].begin();
    ans2 /= Mint(rem2);
  }
  if (rem2 != -1) {
    if (sz(neg[1])) {
      add2 = *neg[1].rbegin();
      ans2 *= Mint(add2);
      ans2_valid = true;
    } else if (zero) {
      add2 = *neg[1].rbegin();
      ans2 *= Mint(add2);
      ans2_valid = true;
    }
  }

  if (ans1_valid && ans2_valid) {
    if (add1 * rem2 >= add2 * rem1) {
      ans = ans1;
    } else {
      ans = ans2;
    }
  } else if (ans1_valid) {
    ans = ans1;
  } else if (ans2_valid) {
    ans = ans2;
  } else if (zero) {
    ans = 0;
  }
  cout << ans.value() << endl;
  return (0 ^ _ ^ 0);
}