Language: C++

#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
#define fi first
#define se second
template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = 0;
//---------------------------------//

int main() {
	int H, W, K;
	cin >> H >> W >> K;
	int stx, sty, edx, edy;
	cin >> sty >> stx >> edy >> edx;
	--sty; --stx; --edy; --edx;
	vector<string> maps(H);
	REP(i, H) cin >> maps[i];
	
	vector<vector<int>> d[4], done[4], kmax[4]; // 直前の移動方向
	REP(i, 4) {
		d[i] = vector<vector<int>>(H, vector<int>(W, INF));
		done[i] = vector<vector<int>>(H, vector<int>(W));
		kmax[i] = vector<vector<int>>(H, vector<int>(W, 0));
	}
	
	struct Data {
		int y, x, pdir, res;
	};
	
	int dx[] = {1,0,-1,0}, dy[] = {0,-1,0,1};
	
	deque<Data> deq;
	REP(dir, 4) {
		d[dir][sty][stx] = 0;
		deq.push_back(Data{sty, stx, dir, 0});
	}
	
	auto ok = [&](int y, int x) {
		return y >= 0 && y < H && x >= 0 && x < W && maps[y][x] == '.';
	};
	
	
	while (!deq.empty()) {
		Data cur = deq.front(); deq.pop_front();
		if (!chmax(done[cur.y][cur.x], 1)) continue;
		
		cur.res = kmax[cur.pdir][cur.y][cur.x];
		
		REP(dir, 4) {
			if (chmin(d[dir][cur.y][cur.x], d[cur.pdir][cur.y][cur.x] + 1)) {
				deq.push_back(Data{cur.y, cur.x, dir, K});
			}
		}
		
		int dir = cur.pdir;
		
		int ny = cur.y + dy[dir], nx = cur.x + dx[dir];
		if (!ok(ny, nx)) continue;
		
		if (cur.res == 0) {
			if (chmin(d[dir][ny][nx], d[cur.pdir][cur.y][cur.x] + 1)) {
				deq.push_back(Data{ny, nx, dir, K - 1});
				kmax[dir][ny][nx] = K - 1;
			}
		}
		else {
			if (chmin(d[dir][ny][nx], d[cur.pdir][cur.y][cur.x])) {
				deq.push_front(Data{ny, nx, dir, cur.res - 1});
			}
			if (d[dir][ny][nx] == d[cur.pdir][cur.y][cur.x]) chmax(kmax[dir][ny][nx], cur.res - 1);
		}
	}
	
	int ans = INF;
	REP(dir, 4) chmin(ans, d[dir][edy][edx]);
	if (ans == INF) puts("-1");
	else cout << ans << endl;
	
	return 0;
}


Compiler output:
a.cc: In instantiation of 'bool chmax(A&, B) [with A = std::vector<int>; B = int]':
a.cc:53:13:   required from here
   53 |                 if (!chmax(done[cur.y][cur.x], 1)) continue;
      |                      ~~~~~^~~~~~~~~~~~~~~~~~~~~~~
a.cc:8:70: error: no match for 'operator<' (operand types are 'std::vector<int>' and 'int')
    8 | template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
      |                                                                     ~^~
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:1143:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1143 |     operator<(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1143:5: note:   template argument deduction/substitution failed:
a.cc:8:70: note:   'std::vector<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
    8 | template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
      |                                                                     ~^~
/usr/include/c++/14/bits/regex.h:1224:5: 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>&)'
 1224 |     operator<(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1224:5: note:   template argument deduction/substitution failed:
a.cc:8:70: note:   'std::vector<int>' is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
    8 | template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
      |                                                                     ~^~
/usr/include/c++/14/bits/regex.h:1317:5: 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>&)'
 1317 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1317:5: note:   template argument deduction/substitution failed:
a.cc:8:70: note:   'std::vector<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
    8 | template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
      |                                                                     ~^~
/usr/include/c++/14/bits/regex.h:1391:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1391 |     operator<(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1391:5: note:   template argument deduction/substitution failed:
a.cc:8:70: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
    8 | template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
      |                                                                     ~^~
/usr/include/c++/14/bits/regex.h:1485:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1485 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1485:5: note:   template argument deduction/substitution failed:
a.cc:8:70: note:   'std::vector<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
    8 | template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
      |                                                                     ~^~
/usr/include/c++/14/bits/regex.h:1560:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1560 |     operator<(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1560:5: note:   template argument deduction/substitution failed:
a.cc:8:70: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
    8 | template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
      |                                                                     ~^~
/usr/include/c++/14/bits/regex.h:1660:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1660 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1660:5: note:   template argument deduction/substitution failed:
a.cc:8:70: note:   'std::vector<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
    8 | template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
      |                                                                     ~^~
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:1045:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator<(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1045 |     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1045:5: note:   template argument deduction/substitution failed:
a.cc:8:70: note:   'std::vector<int>' is not derived from 'const std::pair<_T1, _T2>'
    8 | template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
      |                                                                     ~^~
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:448:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  448 |     operator<(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:448:5: note:   template argument deduction/substitution failed:
a.cc:8:70: note:   'std::vector<int>' is not derived from 'const std::reverse_iterator<_Iterator>'
    8 | template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
      |                                                                     ~^~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  493 |     operator<(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note:   template argument deduction/substitution failed:
a.cc:8:70: note:   'std::vector<int>' is not derived from 'const std::reverse_iterator<_Iterator>'
    8 | template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
      |                                                                     ~^~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1694 |     operator<(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note:   template argument deduction/substitution failed:
a.cc:8:70: note:   'std::vector<int>' is not derived from 'const std::move_iterator<_IteratorL>'
    8 | template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
      |                                                                     ~^~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1760 |     operator<(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note:   template argument deduction/substitution failed:
a.cc:8:70: note:   'std::vector<int>' is not derived from 'const std::move_iterator<_IteratorL>'
    8 | template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
      |                                                                     ~^~
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 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:
/usr/include/c++/14/string_view:673:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  673 |     operator< (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:673:5: note:   template argument deduction/substitution failed:
a.cc:8:70: note:   'std::vector<int>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
    8 | template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
      |                                                                     ~^~
/usr/include/c++/14/string_view:680:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _