Problem p02616 (C++)

Buggy submission (status: Runtime Error):
#define _CRT_SECURE_NO_WARNINGS
#pragma GCC target("avx")
#pragma GCC optimize("O3")
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string.h>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
#define rep(i, n) for (int i = 0; i < (lint)(n); i++)
#define REP(i, n) for (int i = 1; i <= (lint)(n); i++)
#define all(V) V.begin(), V.end()
#define stackReplaceBegin(size)                                                \
  void *p = malloc(size);                                                      \
  esp_new = (lint)p + size - 1;                                                \
  void *stack_extend_memory_ = malloc(size);                                   \
  void *stack_extend_origin_memory_;                                           \
  char *stack_extend_dummy_memory_ = (char *)alloca(                           \
      (1 + (int)(((long long)stack_extend_memory_) & 127)) * 16);              \
  *stack_extend_dummy_memory_ = 0;                                             \
  asm volatile("mov %%rsp, %%rbx\nmov %%rax, %%rsp"                            \
               : "=b"(stack_extend_origin_memory_)                             \
               : "a"((char *)stack_extend_memory_ + (size)-1024));
typedef long long lint;
typedef unsigned long long ulint;
typedef std::pair<int, int> P;
constexpr int INF = INT_MAX / 2;
constexpr lint LINF = LLONG_MAX / 2;
constexpr double eps = DBL_EPSILON;
constexpr double PI = 3.141592653589793238462643383279;
lint esp_new;
template <class T>
class prique : public std::priority_queue<T, std::vector<T>, std::greater<T>> {
};
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;
}
inline lint gcd(lint a, lint b) {
  while (b) {
    lint c = a;
    a = b;
    b = c % b;
  }
  return a;
}
inline lint lcm(lint a, lint b) { return a / gcd(a, b) * b; }
bool isprime(lint n) {
  if (n == 1)
    return false;
  for (int i = 2; i * i <= n; i++) {
    if (n % i == 0)
      return false;
  }
  return true;
}
template <typename T> T mypow(T a, unsigned int b) {
  T res(1), now(a);
  while (b) {
    if (b & 1)
      res *= now;
    b >>= 1;
    now *= now;
  }
  return res;
}
template <typename T> void printArray(std::vector<T> &vec) {
  rep(i, (int)vec.size() - 1) std::cout << vec[i] << " ";
  if (!vec.empty())
    std::cout << vec.back() << std::endl;
}
template <typename T> void printArray(T l, T r) {
  T rprev = r;
  rprev--;
  for (T i = l; i != rprev; i++) {
    std::cout << *i << " ";
  }
  std::cout << *rprev << std::endl;
}
class ModInt {
  lint value;

public:
  static const unsigned int modulo;
  ModInt() : value(0) {}
  template <typename T> ModInt(T value = 0) : value(value) {
    if (value < 0)
      value = -(lint)(-value % modulo) + modulo;
    this->value = value % modulo;
  }
  inline operator int() const { return value; }
  inline ModInt &operator+=(const ModInt &x) {
    value += x.value;
    if (value >= modulo)
      value -= modulo;
    return *this;
  }
  inline ModInt &operator++() {
    if (value == modulo - 1)
      value = 0;
    else
      value++;
    return *this;
  }
  inline ModInt operator-() const { return ModInt(0) -= *this; }
  inline ModInt &operator-=(const ModInt &x) {
    value -= x.value;
    if (value < 0)
      value += modulo;
    return *this;
  }
  inline ModInt &operator--() {
    if (value == 0)
      value = modulo - 1;
    else
      value--;
    return *this;
  }
  inline ModInt &operator*=(const ModInt &x) {
    value = value * x.value % modulo;
    return *this;
  }
  inline ModInt &operator/=(ModInt rhs) {
    int exp = modulo - 2;
    while (exp) {
      if (exp & 1)
        *this *= rhs;
      rhs *= rhs;
      exp >>= 1;
    }
    return *this;
  }
  template <typename T> ModInt operator+(const T &rhs) const {
    return ModInt(*this) += rhs;
  }
  template <typename T> ModInt &operator+=(const T &rhs) {
    return operator+=(ModInt(rhs));
  }
  template <typename T> ModInt operator-(const T &rhs) const {
    return ModInt(*this) -= rhs;
  }
  template <typename T> ModInt &operator-=(const T &rhs) {
    return operator-=(ModInt(rhs));
  }
  template <typename T> ModInt operator*(const T &rhs) const {
    return ModInt(*this) *= rhs;
  }
  template <typename T> ModInt &operator*=(const T &rhs) {
    return operator*=(ModInt(rhs));
  }
  template <typename T> ModInt operator/(const T &rhs) const {
    return ModInt(*this) /= rhs;
  }
  template <typename T> ModInt &operator/=(const T &rhs) {
    return operator/=(ModInt(rhs));
  }
};
std::istream &operator>>(std::istream &ist, ModInt &x) {
  lint a;
  ist >> a;
  x = a;
  return ist;
}
const unsigned int ModInt::modulo = 1000000007;
lint n, k, a[200010], zero;
std::vector<lint> vec[2];
int main() {
  std::cin >> n >> k;
  rep(i, n) {
    std::cin >> a[i];
    if (a[i] < 0)
      vec[0].push_back(-a[i]);
    else if (a[i] > 0)
      vec[1].push_back(a[i]);
    else
      zero++;
  }
  std::sort(all(vec[0]), std::greater<lint>());
  std::sort(all(vec[1]), std::greater<lint>());
  if (zero == 0) {
    ModInt ans = 1;
    if (vec[1].empty() && k % 2) {
      std::reverse(all(vec[0]));
      ans = -1;
      rep(i, k) ans *= vec[0][i];
    } else if (k == n && vec[0].size() % 2) {
      rep(i, n) ans *= a[i];
    } else {
      int x = std::min(k, (lint)vec[0].size()) / 2 * 2;
      rep(i, x) ans *= vec[0][i];
      rep(i, k - x) ans *= vec[1][i];
      while (x && k - x + 1 < vec[1].size()) {
        if (vec[0][x - 1] * vec[0][x - 2] > vec[1][k - x] * vec[1][k - x + 1])
          break;
        ans /= vec[0][x - 1];
        ans /= vec[0][x - 2];
        ans *= vec[1][k - x];
        ans *= vec[1][k - x + 1];
        x -= 2;
      }
    }
    std::cout << ans << std::endl;
  } else {
    if (vec[0].size() + vec[1].size() < k)
      std::cout << 0 << std::endl;
    else if (vec[0].size() + vec[1].size() == k && vec[0].size() % 2)
      std::cout << 0 << std::endl;
    else {
      ModInt ans = 1;
      int x = std::min(k, (lint)vec[0].size()) / 2 * 2;
      rep(i, x) ans *= vec[0][i];
      rep(i, k - x) ans *= vec[1][i];
      while (x && k - x + 1 < vec[1].size()) {
        if (vec[0][x - 1] * vec[0][x - 2] > vec[1][k - x] * vec[1][k - x + 1])
          break;
        ans /= vec[0][x - 1];
        ans /= vec[0][x - 2];
        ans *= vec[1][k - x];
        ans *= vec[1][k - x + 1];
        x -= 2;
      }
      std::cout << ans << std::endl;
    }
  }
  return 0;
}

Fixed submission:
#define _CRT_SECURE_NO_WARNINGS
#pragma GCC target("avx")
#pragma GCC optimize("O3")
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string.h>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
#define rep(i, n) for (int i = 0; i < (lint)(n); i++)
#define REP(i, n) for (int i = 1; i <= (lint)(n); i++)
#define all(V) V.begin(), V.end()
#define stackReplaceBegin(size)                                                \
  void *p = malloc(size);                                                      \
  esp_new = (lint)p + size - 1;                                                \
  void *stack_extend_memory_ = malloc(size);                                   \
  void *stack_extend_origin_memory_;                                           \
  char *stack_extend_dummy_memory_ = (char *)alloca(                           \
      (1 + (int)(((long long)stack_extend_memory_) & 127)) * 16);              \
  *stack_extend_dummy_memory_ = 0;                                             \
  asm volatile("mov %%rsp, %%rbx\nmov %%rax, %%rsp"                            \
               : "=b"(stack_extend_origin_memory_)                             \
               : "a"((char *)stack_extend_memory_ + (size)-1024));
typedef long long lint;
typedef unsigned long long ulint;
typedef std::pair<int, int> P;
constexpr int INF = INT_MAX / 2;
constexpr lint LINF = LLONG_MAX / 2;
constexpr double eps = DBL_EPSILON;
constexpr double PI = 3.141592653589793238462643383279;
lint esp_new;
template <class T>
class prique : public std::priority_queue<T, std::vector<T>, std::greater<T>> {
};
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;
}
inline lint gcd(lint a, lint b) {
  while (b) {
    lint c = a;
    a = b;
    b = c % b;
  }
  return a;
}
inline lint lcm(lint a, lint b) { return a / gcd(a, b) * b; }
bool isprime(lint n) {
  if (n == 1)
    return false;
  for (int i = 2; i * i <= n; i++) {
    if (n % i == 0)
      return false;
  }
  return true;
}
template <typename T> T mypow(T a, unsigned int b) {
  T res(1), now(a);
  while (b) {
    if (b & 1)
      res *= now;
    b >>= 1;
    now *= now;
  }
  return res;
}
template <typename T> void printArray(std::vector<T> &vec) {
  rep(i, (int)vec.size() - 1) std::cout << vec[i] << " ";
  if (!vec.empty())
    std::cout << vec.back() << std::endl;
}
template <typename T> void printArray(T l, T r) {
  T rprev = r;
  rprev--;
  for (T i = l; i != rprev; i++) {
    std::cout << *i << " ";
  }
  std::cout << *rprev << std::endl;
}
class ModInt {
  lint value;

public:
  static const unsigned int modulo;
  ModInt() : value(0) {}
  template <typename T> ModInt(T value = 0) : value(value) {
    if (value < 0)
      value = -(lint)(-value % modulo) + modulo;
    this->value = value % modulo;
  }
  inline operator int() const { return value; }
  inline ModInt &operator+=(const ModInt &x) {
    value += x.value;
    if (value >= modulo)
      value -= modulo;
    return *this;
  }
  inline ModInt &operator++() {
    if (value == modulo - 1)
      value = 0;
    else
      value++;
    return *this;
  }
  inline ModInt operator-() const { return ModInt(0) -= *this; }
  inline ModInt &operator-=(const ModInt &x) {
    value -= x.value;
    if (value < 0)
      value += modulo;
    return *this;
  }
  inline ModInt &operator--() {
    if (value == 0)
      value = modulo - 1;
    else
      value--;
    return *this;
  }
  inline ModInt &operator*=(const ModInt &x) {
    value = value * x.value % modulo;
    return *this;
  }
  inline ModInt &operator/=(ModInt rhs) {
    int exp = modulo - 2;
    while (exp) {
      if (exp & 1)
        *this *= rhs;
      rhs *= rhs;
      exp >>= 1;
    }
    return *this;
  }
  template <typename T> ModInt operator+(const T &rhs) const {
    return ModInt(*this) += rhs;
  }
  template <typename T> ModInt &operator+=(const T &rhs) {
    return operator+=(ModInt(rhs));
  }
  template <typename T> ModInt operator-(const T &rhs) const {
    return ModInt(*this) -= rhs;
  }
  template <typename T> ModInt &operator-=(const T &rhs) {
    return operator-=(ModInt(rhs));
  }
  template <typename T> ModInt operator*(const T &rhs) const {
    return ModInt(*this) *= rhs;
  }
  template <typename T> ModInt &operator*=(const T &rhs) {
    return operator*=(ModInt(rhs));
  }
  template <typename T> ModInt operator/(const T &rhs) const {
    return ModInt(*this) /= rhs;
  }
  template <typename T> ModInt &operator/=(const T &rhs) {
    return operator/=(ModInt(rhs));
  }
};
std::istream &operator>>(std::istream &ist, ModInt &x) {
  lint a;
  ist >> a;
  x = a;
  return ist;
}
const unsigned int ModInt::modulo = 1000000007;
lint n, k, a[200010], zero;
std::vector<lint> vec[2];
int main() {
  std::cin >> n >> k;
  rep(i, n) {
    std::cin >> a[i];
    if (a[i] < 0)
      vec[0].push_back(-a[i]);
    else if (a[i] > 0)
      vec[1].push_back(a[i]);
    else
      zero++;
  }
  std::sort(all(vec[0]), std::greater<lint>());
  std::sort(all(vec[1]), std::greater<lint>());
  if (zero == 0) {
    ModInt ans = 1;
    if (vec[1].empty() && k % 2) {
      std::reverse(all(vec[0]));
      ans = -1;
      rep(i, k) ans *= vec[0][i];
    } else if (k == n && vec[0].size() % 2) {
      rep(i, n) ans *= a[i];
    } else {
      int x = std::min(k, (lint)vec[0].size()) / 2 * 2;
      rep(i, x) ans *= vec[0][i];
      rep(i, k - x) ans *= vec[1][i];
      while (x && k - x + 1 < vec[1].size()) {
        if (vec[0][x - 1] * vec[0][x - 2] > vec[1][k - x] * vec[1][k - x + 1])
          break;
        ans /= vec[0][x - 1];
        ans /= vec[0][x - 2];
        ans *= vec[1][k - x];
        ans *= vec[1][k - x + 1];
        x -= 2;
      }
    }
    std::cout << ans << std::endl;
  } else {
    if (vec[0].size() + vec[1].size() < k)
      std::cout << 0 << std::endl;
    else if (vec[0].size() + vec[1].size() == k && vec[0].size() % 2)
      std::cout << 0 << std::endl;
    else if (vec[1].empty() && k % 2)
      std::cout << 0 << std::endl;
    else {
      ModInt ans = 1;
      int x = std::min(k, (lint)vec[0].size()) / 2 * 2;
      rep(i, x) ans *= vec[0][i];
      rep(i, k - x) ans *= vec[1][i];
      while (x && k - x + 1 < vec[1].size()) {
        if (vec[0][x - 1] * vec[0][x - 2] > vec[1][k - x] * vec[1][k - x + 1])
          break;
        ans /= vec[0][x - 1];
        ans /= vec[0][x - 2];
        ans *= vec[1][k - x];
        ans *= vec[1][k - x + 1];
        x -= 2;
      }
      std::cout << ans << std::endl;
    }
  }
  return 0;
}