Language: C++

#include <bits/stdc++.h>
using namespace std;

bool special = false;

vector<vector<int>> t;

bool check(const vector<vector<char>> &g) { // checks row ok?
  vector<vector<char>> rows;
  map<vector<char>, int> cnt;
  for (int i = 0; i < g.size(); ++i) {
    rows.emplace_back(g[i]);
    sort(rows.back().begin(), rows.back().end());
    ++cnt[rows.back()];
  }
  int bad = 0;
  for (auto it = cnt.begin(); it != cnt.end(); ++it) {
    bad += it->second & 1;
    if (special) {
      t.emplace_back(it->first);
    }
  }
  return bad <= (g.size() & 1);
}

signed main() {
  ios::sync_with_stdio(false);
  int N, M;
  cin >> N >> M;
  vector<string> G(N);
  for (int i = 0; i < N; ++i) {
    cin >> G[i];
  }
  vector<vector<char>> g(N, vector<char>(M));
  for (int i = 0; i < N; ++i) {
    for (int j = 0; j < M; ++j) {
      g[i][j] = G[i][j];
    }
  }
  if (N & M & 1) {
    special = true;
  }
  bool ok = true;
  ok &= check(g);
  vector<vector<char>> tg(M, vector<char>(N));
  for (int i = 0; i < N; ++i) {
    for (int j = 0; j < M; ++j) {
      tg[j][i] = g[i][j];
    }
  }
  ok &= check(tg);
  if (ok && special) {
    char c = t[0][t[0].size() / 2];
    multiset<int> a, b, c, d;
    for (int i = 0; i < t[0].size(); ++i) {
      if (i < t[0].size() / 2) {
        a.emplace(t[0][i]);
      } else if (i > t[0].size() / 2) {
        b.emplace(t[0][i]);
      }
    }
    for (int i = 0; i < t[1].size(); ++i) {
      if (i < t[1].size() / 2) {
        c.emplace(t[1][i]);
      } else if (i > t[1].size() / 2) {
        d.emplace(t[1][i]);
      }
    }
    if (a != b || c != d) ok = false;
  }
  cout << (ok ? "YES" : "NO") << endl;
  return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:54:25: error: conflicting declaration 'std::multiset<int> c'
   54 |     multiset<int> a, b, c, d;
      |                         ^
a.cc:53:10: note: previous declaration as 'char c'
   53 |     char c = t[0][t[0].size() / 2];
      |          ^
a.cc:64:11: error: request for member 'emplace' in 'c', which is of non-class type 'char'
   64 |         c.emplace(t[1][i]);
      |           ^~~~~~~
a.cc:69:21: error: no match for 'operator!=' (operand types are 'char' and 'std::multiset<int>')
   69 |     if (a != b || c != d) ok = false;
      |                   ~ ^~ ~
      |                   |    |
      |                   char std::multiset<int>
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:1:
/usr/include/c++/14/bits/regex.h:1132:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator!=(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1132 |     operator!=(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1132:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'char'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
/usr/include/c++/14/bits/regex.h:1212:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator!=(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1212 |     operator!=(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1212:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   mismatched types 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>' and 'char'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
/usr/include/c++/14/bits/regex.h:1305:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator!=(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1305 |     operator!=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1305:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'char'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
/usr/include/c++/14/bits/regex.h:1379:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator!=(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1379 |     operator!=(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1379:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   'std::multiset<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
/usr/include/c++/14/bits/regex.h:1473:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator!=(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1473 |     operator!=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1473:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'char'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
/usr/include/c++/14/bits/regex.h:1547:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator!=(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1547 |     operator!=(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1547:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   'std::multiset<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
/usr/include/c++/14/bits/regex.h:1647:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator!=(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1647 |     operator!=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1647:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'char'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
/usr/include/c++/14/bits/regex.h:2213:5: note: candidate: 'template<class _Bi_iter, class _Alloc> bool std::__cxx11::operator!=(const match_results<_BiIter, _Alloc>&, const match_results<_BiIter, _Alloc>&)'
 2213 |     operator!=(const match_results<_Bi_iter, _Alloc>& __m1,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:2213:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   mismatched types 'const std::__cxx11::match_results<_BiIter, _Alloc>' and 'char'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_pair.h:1052:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator!=(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1052 |     operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1052:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   mismatched types 'const std::pair<_T1, _T2>' and 'char'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:455:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator!=(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  455 |     operator!=(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:455:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'char'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
/usr/include/c++/14/bits/stl_iterator.h:500:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator!=(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  500 |     operator!=(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:500:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'char'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
/usr/include/c++/14/bits/stl_iterator.h:1686:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator!=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1686 |     operator!=(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1686:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'char'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
/usr/include/c++/14/bits/stl_iterator.h:1753:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator!=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1753 |     operator!=(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1753:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'char'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
In file included from /usr/include/c++/14/bits/char_traits.h:42,
                 from /usr/include/c++/14/string:42,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/bits/postypes.h:197:5: note: candidate: 'template<class _StateT> bool std::operator!=(const fpos<_StateT>&, const fpos<_StateT>&)'
  197 |     operator!=(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/postypes.h:197:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   mismatched types 'const std::fpos<_StateT>' and 'char'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
In file included from /usr/include/c++/14/string:43:
/usr/include/c++/14/bits/allocator.h:243:5: note: candidate: 'template<class _T1, class _T2> bool std::operator!=(const allocator<_CharT>&, const allocator<_T2>&)'
  243 |     operator!=(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/14/bits/allocator.h:243:5: note:   template argument deduction/substitution failed:
a.cc:69:24: note:   mismatched types 'const std::allocator<_CharT>' and 'char'
   69 |     if (a != b || c != d) ok = false;
      |                        ^
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54:
/usr/include/c++/14/string_view:651:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator!=(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  651 |     operator!=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:651:5: note:   template argument