Language: C++

    #include<iostream>
    #include<stdio.h>
    //#include <bits/stdc++.h>
    #include<vector>
    #include<float.h>
    #include<iomanip>
    #include<algorithm>
    #include<string>
    #include<cstring>
    #include<math.h>
    #include<cmath>
    #include<sstream>
    #include<set>
    #include<map>
    #include<queue>
    #include<cassert>
    #include<cmath>
    #include<cstdint>
     
    #define INF 1e9
    #define rep(i,n)for(int i=0;(i)<(int)(n);i++)
    #define REP(i,a,b)for(int i=(int)(a);(i)<=(int)(b);i++)
    #define VEC(type, c, n) std::vector<type> c(n);for(auto& i:c)std::cin>>i;
    #define vec(type,n) vector<type>(n)
    #define vvec(m,n) vector<vector<int>> (int(m),vector<int>(n))
    #define ALL(a)  (a).begin(),(a).end()
     
    using namespace std;
    using ll = long long;
    using Graph = vector<vector<int>>;
    using P = pair<ll, ll>;
     
//const ll MOD = INF + 7;
//Combination MOD
const int MOD = 1e9 + 7;

//bit全探索
vector<int>bitSearch(int bit,int n){
    vector<int>S;
    rep(i,n)if(bit&(1<<i))S.push_back(i);
    S.push_back(1e9);
    return S;
}

int main(){
   int n, k;
   cin >> n >> k;
   int zr = 0;
   vector<ll> a(n), mn, pl;
   rep(i, n){
      cin >> a[i];
      if(a[i] < 0)mn.push_back(a[i]);
      else pl.push_back(a[i]);
   }
   sort(ALL(mn));
   sort(ALL(pl), greater<ll>());
   

   int ms = mn.size(), ps = pl.size();

   if(n == k){
      ll r = 1;
      rep(i, ps){
         r = (r * pl[i]) % MOD;
         if(r < 0)r += MOD;
      }
      rep(i, ms){
         r = (r * mn[i]) % MOD;
         if(r < 0)r += MOD;
      }
      if(r < 0)r += MOD;
      cout << r << endl;
      return 0;
   }
   //答えがmnになるとき
   if(ps == 0 && k % 2 == 1){
      ll r = 1;
      reverse(ALL(mn));
      rep(i, k){
         r = r * mn[i];
         r %= MOD;
         if(r < 0)r += MOD;
         r %= MOD;
      }
      if(r < MOD)r += MOD;
      r %= MOD;
      cout << r << endl;
      return 0;
   }

   if(ps == 0 && k % 2 == 0){
      ll r = 1;
      //reverse(ALL(mn));
      rep(i, k){
         r = r * mn[i];
         r %= MOD;
         if(r < 0)r += MOD;
         r %= MOD;
      }
      if(r < MOD)r += MOD;
      r %= MOD;
      cout << r << endl;
      return 0;
   }

   //絶対pls
   //mnの累積積

   vector<P> abso(n);
   rep(i, n){
      if(a[i] < 0)abso[i] = P(abs(a[i]), 1);
      else abso[i] = P(abs(abso[i]), 0);
   }
   sort(ALL(abso), greater<ll>());
   vector<int> fugou(n);
   rep(i, n)fugou[i] = abso[i].second;
   int case1 = -1, case2 = -1;
   for(int i = k - 1; i >= 0; i--){
      if(case1 < 0 && abso[i].second == 1)case1 = i;
      if(case2 < 0 %% abso[i].first == 0)case2 = i;
   }

   ll r = 1, cnt = 0;
   rep(i, n){
      if(i == case1)continue;
      if(i >= k && abso[i].second == 1)continue;
      r = (r * abso[i].first) % MOD;
      if(r < 0)r += MOD;
      cnt++;
      if(cnt == k)break;
   }
   ll l = 1, cnt = 0;
   rep(i, n){
      if(i == case2)continue;
      if(i >= k && abso[i].second == 0)continue;
      l = (l * abso[i].first) % MOD;
      if(l < 0)l += MOD;
      cnt++;
      if(cnt == k)break;
   }
   ll res = max(l, r);
   cout << res << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:112:27: error: no matching function for call to 'abs(__gnu_cxx::__alloc_traits<std::allocator<std::pair<long long int, long long int> >, std::pair<long long int, long long int> >::value_type&)'
  112 |       else abso[i] = P(abs(abso[i]), 0);
      |                        ~~~^~~~~~~~~
In file included from /usr/include/c++/14/cstdlib:79,
                 from /usr/include/c++/14/ext/string_conversions.h:43,
                 from /usr/include/c++/14/bits/basic_string.h:4154,
                 from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/stdlib.h:980:12: note: candidate: 'int abs(int)'
  980 | extern int abs (int __x) __THROW __attribute__ ((__const__)) __wur;
      |            ^~~
/usr/include/stdlib.h:980:21: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<std::pair<long long int, long long int> >, std::pair<long long int, long long int> >::value_type' {aka 'std::pair<long long int, long long int>'} to 'int'
  980 | extern int abs (int __x) __THROW __attribute__ ((__const__)) __wur;
      |                 ~~~~^~~
In file included from /usr/include/c++/14/cstdlib:81:
/usr/include/c++/14/bits/std_abs.h:137:3: note: candidate: 'constexpr __float128 std::abs(__float128)'
  137 |   abs(__float128 __x)
      |   ^~~
/usr/include/c++/14/bits/std_abs.h:137:18: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<std::pair<long long int, long long int> >, std::pair<long long int, long long int> >::value_type' {aka 'std::pair<long long int, long long int>'} to '__float128'
  137 |   abs(__float128 __x)
      |       ~~~~~~~~~~~^~~
/usr/include/c++/14/bits/std_abs.h:85:3: note: candidate: 'constexpr __int128 std::abs(__int128)'
   85 |   abs(__GLIBCXX_TYPE_INT_N_0 __x) { return __x >= 0 ? __x : -__x; }
      |   ^~~
/usr/include/c++/14/bits/std_abs.h:85:30: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<std::pair<long long int, long long int> >, std::pair<long long int, long long int> >::value_type' {aka 'std::pair<long long int, long long int>'} to '__int128'
   85 |   abs(__GLIBCXX_TYPE_INT_N_0 __x) { return __x >= 0 ? __x : -__x; }
      |                              ^
/usr/include/c++/14/bits/std_abs.h:79:3: note: candidate: 'constexpr long double std::abs(long double)'
   79 |   abs(long double __x)
      |   ^~~
/usr/include/c++/14/bits/std_abs.h:79:19: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<std::pair<long long int, long long int> >, std::pair<long long int, long long int> >::value_type' {aka 'std::pair<long long int, long long int>'} to 'long double'
   79 |   abs(long double __x)
      |       ~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/std_abs.h:75:3: note: candidate: 'constexpr float std::abs(float)'
   75 |   abs(float __x)
      |   ^~~
/usr/include/c++/14/bits/std_abs.h:75:13: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<std::pair<long long int, long long int> >, std::pair<long long int, long long int> >::value_type' {aka 'std::pair<long long int, long long int>'} to 'float'
   75 |   abs(float __x)
      |       ~~~~~~^~~
/usr/include/c++/14/bits/std_abs.h:71:3: note: candidate: 'constexpr double std::abs(double)'
   71 |   abs(double __x)
      |   ^~~
/usr/include/c++/14/bits/std_abs.h:71:14: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<std::pair<long long int, long long int> >, std::pair<long long int, long long int> >::value_type' {aka 'std::pair<long long int, long long int>'} to 'double'
   71 |   abs(double __x)
      |       ~~~~~~~^~~
/usr/include/c++/14/bits/std_abs.h:61:3: note: candidate: 'long long int std::abs(long long int)'
   61 |   abs(long long __x) { return __builtin_llabs (__x); }
      |   ^~~
/usr/include/c++/14/bits/std_abs.h:61:17: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<std::pair<long long int, long long int> >, std::pair<long long int, long long int> >::value_type' {aka 'std::pair<long long int, long long int>'} to 'long long int'
   61 |   abs(long long __x) { return __builtin_llabs (__x); }
      |       ~~~~~~~~~~^~~
/usr/include/c++/14/bits/std_abs.h:56:3: note: candidate: 'long int std::abs(long int)'
   56 |   abs(long __i) { return __builtin_labs(__i); }
      |   ^~~
/usr/include/c++/14/bits/std_abs.h:56:12: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<std::pair<long long int, long long int> >, std::pair<long long int, long long int> >::value_type' {aka 'std::pair<long long int, long long int>'} to 'long int'
   56 |   abs(long __i) { return __builtin_labs(__i); }
      |       ~~~~~^~~
a.cc:120:21: error: expected primary-expression before '%' token
  120 |       if(case2 < 0 %% abso[i].first == 0)case2 = i;
      |                     ^
a.cc:132:14: error: redeclaration of 'll cnt'
  132 |    ll l = 1, cnt = 0;
      |              ^~~
a.cc:123:14: note: 'll cnt' previously declared here
  123 |    ll r = 1, cnt = 0;
      |              ^~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:71,
                 from /usr/include/c++/14/string:51:
/usr/include/c++/14/bits/predefined_ops.h: In instantiation of 'constexpr bool __gnu_cxx::__ops::_Iter_comp_iter<_Compare>::operator()(_Iterator1, _Iterator2) [with _Iterator1 = __gnu_cxx::__normal_iterator<std::pair<long long int, long long int>*, std::vector<std::pair<long long int, long long int> > >; _Iterator2 = __gnu_cxx::__normal_iterator<std::pair<long long int, long long int>*, std::vector<std::pair<long long int, long long int> > >; _Compare = std::greater<long long int>]':
/usr/include/c++/14/bits/stl_algo.h:1777:14:   required from 'void std::__insertion_sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<pair<long long int, long long int>*, vector<pair<long long int, long long int> > >; _Compare = __gnu_cxx::__ops::_Iter_comp_iter<greater<long long int> >]'
 1777 |           if (__comp(__i, __first))
      |               ~~~~~~^~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algo.h:1817:25:   required from 'void std::__final_insertion_sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<pair<long long int, long long int>*, vector<pair<long long int, long long int> > >; _Compare = __gnu_cxx::__ops::_Iter_comp_iter<greater<long long int> >]'
 1817 |           std::__insertion_sort(__first, __first + int(_S_threshold), __comp);
      |           ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algo.h:1908:31:   required from 'void std::__sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<pair<long long int, long long int>*, vector<pair<long long int, long long int> > >; _Compare = __gnu_cxx::__ops::_Iter_comp_iter<greater<long long int> >]'
 1908 |           std::__final_insertion_sort(__first, __last, __comp);
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algo.h:4805:18:   required from 'void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<pair<long long int, long long int>*, vector<pair<long long int, long long int> > >; _Compare = greater<long long int>]'
 4805 |       std::__sort(__first, __last, __gnu_cxx::__ops::__iter_comp_iter(__comp));
      |       ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
a.cc:114:8:   required from here
  114 |    sort(ALL(abso), greater<ll>());
      |    ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/predefined_ops.h:158:30: error: no match for call to '(std::greater<long long int>) (std::pair<long long int, long long int>&, std::pair<long long int, long long int>&)'
  158 |         { return bool(_M_comp(*__it1, *__it2)); }
      |                       ~~~~~~~^~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/string:49:
/usr/include/c++/14/bits/stl_function.h:394:7: note: candidate: 'constexpr bool std::greater<_Tp>::operator()(const _Tp&, const _Tp&) const [with _Tp = long long int]'
  394 |       operator()(const _Tp& __x, const _Tp& __y) const
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_function.h:394:29: note:   no known conversion for argument 1 from 'std::pair<long long int, long long int>' to 'const long long int&'
  394 |       operator()(const _Tp& __x, const _Tp& __y) const
      |                  ~~~~~~~~~~~^~~
/usr/include/c++/14/bits/predefined_ops.h: In instantiation of 'bool __gnu_cxx::__ops::_Val_comp_iter<_Compare>::operator()(_Value&, _Iterator) [with _Value = std::pair<long long int, long long int>; _Iterator = __gnu_cxx::__normal_iterator<std::pair<long long int, long long int>*, std::vector<std::pair<long long int, long long int> > >; _Compare = std::greater<long long int>]':
/usr/include/c++/14/bits/stl_algo.h:1757:20:   required from 'void std::__unguarded_linear_insert(_RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<pair<long long int, long long int>*, vector<pair<long long int, long long int> > >; _Compare = __gnu_cxx::__ops::_Val_comp_iter<greater<long long int> >]'
 1757 |       while (__comp(__val, __next))
      |              ~~~~~~^~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algo.h:1785:36:   required from 'void std::__insertion_sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<pair<long long int, long long int>*, vector<pair<long long int, long long int> > >; _Compare = __gnu_cxx::__ops::_Iter_comp_iter<greater<long long int> >]'
 1785 |             std::__unguarded_linear_inse