Language: C++

#include<bits/stdc++.h>
#define rep(i,n)for(int i=0;i<n;i++)
using namespace std;

struct st {
	int x, y;
	char c;
};
bool operator<(st a, st b) {
	if (a.x == b.x&&a.y == b.y)return a.c < b.c;
	if (a.x == b.x)return a.y < b.y;
	return a.x < b.x;
}
char s[1000][1001], f[2][3];
int main() {
	int m, n; scanf("%d%d", &m, &n);
	rep(i, m)scanf("%s", s[i]);
	rep(i, 2)scanf("%s", f[i]);
	map<st, int>mp;
	int ans = 0;
	rep(i, m - 1) {
		rep(j, n - 1) {
			bool match[4]{};
			rep(k, 2)rep(t, 2) {
				if (s[i + k][j + t] == f[k][t])
					match[k * 2 + t] = true;
			}
			int cnt = count(match, match + 4, true);
			if (cnt == 4)ans++;
			if (cnt == 3) {
				rep(k, 4) {
					if (!match[k])
						mp[{i + k / 2, j + k % 2, f[k / 2][k % 2]}]++;
				}
			}
		}
	}
	int Max = 0;
	for (auto p : mp) {
		int cnt = 0;
		rep(i, 2)rep(j, 2) {
			int x = p.first.x + i, y = p.first.y + j;
			bool ok = true;
			rep(k, 2)rep(t, 2) {
				if (s[x + k][y + t] != f[k][t])ok = false;
			}
			if (ok) {
				swap(s[p.first.x][p.first.y], (char)p.first.c);
				if (s[p.first.x][p.first.y] != f[i][j])cnt++;
				swap(s[p.first.x][p.first.y], (char)p.first.c);
			}
		}
		Max = max(Max, p.second - cnt);
	}
	printf("%d\n", ans + Max);
}

Compiler output:
a.cc: In function 'int main()':
a.cc:48:37: error: no matching function for call to 'swap(char&, char)'
   48 |                                 swap(s[p.first.x][p.first.y], (char)p.first.c);
      |                                 ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/bits/stl_pair.h:61,
                 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,
                 from a.cc:1:
/usr/include/c++/14/bits/move.h:226:5: note: candidate: 'std::_Require<std::__not_<std::__is_tuple_like<_Tp> >, std::is_move_constructible<_Tp>, std::is_move_assignable<_Tp> > std::swap(_Tp&, _Tp&) [with _Tp = char; _Require<__not_<__is_tuple_like<_Tp> >, is_move_constructible<_Tp>, is_move_assignable<_Tp> > = void]' (near match)
  226 |     swap(_Tp& __a, _Tp& __b)
      |     ^~~~
/usr/include/c++/14/bits/move.h:226:5: note:   conversion of argument 2 would be ill-formed:
a.cc:48:63: error: cannot bind non-const lvalue reference of type 'char&' to an rvalue of type 'char'
   48 |                                 swap(s[p.first.x][p.first.y], (char)p.first.c);
      |                                                               ^~~~~~~~~~~~~~~
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:77:
/usr/include/c++/14/any:430:15: note: candidate: 'void std::swap(any&, any&)' (near match)
  430 |   inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); }
      |               ^~~~
/usr/include/c++/14/any:430:15: note:   conversion of argument 2 would be ill-formed:
a.cc:48:63: error: cannot bind non-const lvalue reference of type 'std::any&' to an rvalue of type 'std::any'
   48 |                                 swap(s[p.first.x][p.first.y], (char)p.first.c);
      |                                                               ^~~~~~~~~~~~~~~
/usr/include/c++/14/any:191:7: note:   after user-defined conversion: 'std::any::any(_Tp&&) [with _Tp = char; _VTp = char; _Mgr = _Manager_internal<char>; typename std::enable_if<(is_copy_constructible_v<_VTp> && (! __is_in_place_type_v<_VTp>)), bool>::type <anonymous> = true]'
  191 |       any(_Tp&& __value)
      |       ^~~
In file included from /usr/include/c++/14/exception:166,
                 from /usr/include/c++/14/stdexcept:38,
                 from /usr/include/c++/14/system_error:43,
                 from /usr/include/c++/14/bits/ios_base.h:46,
                 from /usr/include/c++/14/streambuf:43,
                 from /usr/include/c++/14/bits/streambuf_iterator.h:35,
                 from /usr/include/c++/14/iterator:66,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:54:
/usr/include/c++/14/bits/exception_ptr.h:229:5: note: candidate: 'void std::__exception_ptr::swap(exception_ptr&, exception_ptr&)'
  229 |     swap(exception_ptr& __lhs, exception_ptr& __rhs)
      |     ^~~~
/usr/include/c++/14/bits/exception_ptr.h:229:25: note:   no known conversion for argument 1 from 'char' to 'std::__exception_ptr::exception_ptr&'
  229 |     swap(exception_ptr& __lhs, exception_ptr& __rhs)
      |          ~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/14/future:51,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:176:
/usr/include/c++/14/bits/std_thread.h:328:3: note: candidate: 'void std::swap(thread&, thread&)'
  328 |   swap(thread& __x, thread& __y) noexcept
      |   ^~~~
/usr/include/c++/14/bits/std_thread.h:328:16: note:   no known conversion for argument 1 from 'char' to 'std::thread&'
  328 |   swap(thread& __x, thread& __y) noexcept
      |        ~~~~~~~~^~~
In file included from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/sstream:1204:5: note: candidate: 'template<class _CharT, class _Traits, class _Allocator> void std::__cxx11::swap(basic_stringbuf<_CharT, _Traits, _Alloc>&, basic_stringbuf<_CharT, _Traits, _Alloc>&)'
 1204 |     swap(basic_stringbuf<_CharT, _Traits, _Allocator>& __x,
      |     ^~~~
/usr/include/c++/14/sstream:1204:5: note:   template argument deduction/substitution failed:
a.cc:48:37: note:   mismatched types 'std::__cxx11::basic_stringbuf<_CharT, _Traits, _Alloc>' and 'char'
   48 |                                 swap(s[p.first.x][p.first.y], (char)p.first.c);
      |                                 ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/sstream:1212:5: note: candidate: 'template<class _CharT, class _Traits, class _Allocator> void std::__cxx11::swap(basic_istringstream<_CharT, _Traits, _Allocator>&, basic_istringstream<_CharT, _Traits, _Allocator>&)'
 1212 |     swap(basic_istringstream<_CharT, _Traits, _Allocator>& __x,
      |     ^~~~
/usr/include/c++/14/sstream:1212:5: note:   template argument deduction/substitution failed:
a.cc:48:37: note:   mismatched types 'std::__cxx11::basic_istringstream<_CharT, _Traits, _Allocator>' and 'char'
   48 |                                 swap(s[p.first.x][p.first.y], (char)p.first.c);
      |                                 ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/sstream:1219:5: note: candidate: 'template<class _CharT, class _Traits, class _Allocator> void std::__cxx11::swap(basic_ostringstream<_CharT, _Traits, _Allocator>&, basic_ostringstream<_CharT, _Traits, _Allocator>&)'
 1219 |     swap(basic_ostringstream<_CharT, _Traits, _Allocator>& __x,
      |     ^~~~
/usr/include/c++/14/sstream:1219:5: note:   template argument deduction/substitution failed:
a.cc:48:37: note:   mismatched types 'std::__cxx11::basic_ostringstream<_CharT, _Traits, _Allocator>' and 'char'
   48 |                                 swap(s[p.first.x][p.first.y], (char)p.first.c);
      |                                 ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/sstream:1226:5: note: candidate: 'template<class _CharT, class _Traits, class _Allocator> void std::__cxx11::swap(basic_stringstream<_CharT, _Traits, _Allocator>&, basic_stringstream<_CharT, _Traits, _Allocator>&)'
 1226 |     swap(basic_stringstream<_CharT, _Traits, _Allocator>& __x,
      |     ^~~~
/usr/include/c++/14/sstream:1226:5: note:   template argument deduction/substitution failed:
a.cc:48:37: note:   mismatched types 'std::__cxx11::basic_stringstream<_CharT, _Traits, _Allocator>' and 'char'
   48 |                                 swap(s[p.first.x][p.first.y], (char)p.first.c);
      |                                 ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181:
/usr/include/c++/14/bits/regex.h:896:5: note: candidate: 'template<class _Ch_type, class _Rx_traits> void std::__cxx11::swap(basic_regex<_Ch_type, _Rx_traits>&, basic_regex<_Ch_type, _Rx_traits>&)'
  896 |     swap(basic_regex<_Ch_type, _Rx_traits>& __lhs,
      |     ^~~~
/usr/include/c++/14/bits/regex.h:896:5: note:   template argument deduction/substitution failed:
a.cc:48:37: note:   mismatched types 'std::__cxx11::basic_regex<_Ch_type, _Rx_traits>' and 'char'
   48 |                                 swap(s[p.first.x][p.first.y], (char)p.first.c);
      |                                 ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/regex.h:2230:5: note: candidate: 'template<class _Bi_iter, class _Alloc> void std::__cxx11::swap(match_results<_BiIter, _Alloc>&, match_results<_BiIter, _Alloc>&)'
 2230 |     swap(match_results<_Bi_iter, _Alloc>& __lhs,
      |     ^~~~
/usr/include/c++/14/bits/regex.h:2230:5: note:   template argument deduction/substitution failed:
a.cc:48:37: note:   mismatched types 'std::__cxx11::match_results<_BiIter, _Alloc>' and 'char'
   48 |                                 swap(s[p.first.x][p.first.y], (char)p.first.c);
      |                                 ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/move.h:250:5: note: candidate: 'template<class _Tp, long unsigned int _Nm> std::__enable_if_t<((bool)std::__is_swappable<_Tp>::value)> std::swap(_Tp (&)[_Nm], _Tp (&)[_Nm])'
  250 |     swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
      |     ^~~~
/usr/include/c++/14/bits/move.h:250:5: note:   template argument deduction/substitution failed:
a.cc:48:37: note:   mismatched types '_Tp [_Nm]' and 'char'
   48 |                                 swap(s[p.first.x][p.first.y], (char)p.first.c);
      |                                 ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1089:5: note: candidate: 'template<class _T1, class _T2> typename std::enable_if<std::__and_<std::__is_swappable<_T1>, std::__is_swappable<_T2> >::value>::type std::swap(pair<_T1, _T2>&, pair<_T1, _T2>&)'
 1089 |     swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y)
      |     ^~~~
/usr/include/c++/14/bits/stl_pair.h:1089:5: note:   template argument deduction/substitution failed:
a.cc:48:37: note:   mismatched types 'std::pair<_T1, _T2>' and 'char'
   48 |                                 swap(s[p.first.x][p.first.y], (char)p.first.c);
      |                                 ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1106:5: note: candidate: 'template<class _T1, class _T2> typename std::enable_if<(! std::__and_<std::__is_swappable<_T1>, std::__is_swappable<_T2> >::value)>::type std::swap(pair<_T1, _T2>&, pair<_T1, _T2>&)' (deleted)
 1106 |     swap(pair<_T1, _T2>&, pair<_T1, _T2>&) = delete;
      |     ^~~~
/usr/include/c++/14/bits/stl_pair.h:1106:5: note:   template argument deduction/substitution failed:
a.cc:48:37: note:   mismatched types 'std::pair<_T1, _T2>' and 'char'
   48 |                                 swap(s[p.first.x][p.first.y], (char)p.first.c);
      |                                 ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52