Language: C++

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

int h, w, k, x1, y1, x2, y2, res;
set<int> row[1000005], col[1000005];
vector<pair<int, int>> visited;
vector<vector<int>> dist, dp1, dp2;
vector<string> grid;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    
    cin >> h >> w >> k >> x1 >> y1 >> x2 >> y2;
    x1--; y1--;
    x2--; y2--;
    grid.resize(h+5);
    dist.assign(h+5, vector<int>(w+5, -1));
    dp1.assign(h+5, vector<int>(w+5, 0));
    dp2.assign(h+5, vector<int>(w+5, 0));
    for (int i = 0; i < h; i++) {
        cin >> grid[i];
        for (int j = 0; j < w; j++) {
            if (grid[i][j] == '.') {
                row[i].insert(j);
                col[j].insert(i);
            }
        }
    }

    for (int i = 0; i < h; i++) {
        for (int j = 0; j < w; j++) {
            if (j) {
                dp1[i][j] = dp1[i][j-1];
            }

            if (grid[i][j] == '@') {
                dp1[i][j]++;
            }
        }
    }

    for (int j = 0; j < w; j++) {
        for (int i = 0; i < h; i++) {
            if (i) {
                dp2[i][j] = dp2[i-1][j];
            }

            if (grid[i][j] == '@') {
                dp2[i][j]++;
            }
        }
    }

    queue<pair<int, int>> q;
    q.push({x1, y1});
    dist[x1][y1] = 0;
    row[x1].erase(y1);
    col[y1].erase(x1);

    while (!q.empty() && dist[x2][y2] == -1) {
        pair<int, int> u = q.front();
        q.pop();

        int target = max(0, u.second - k);
        auto p = row[u.first].lower_bound(target);

        for (auto it = p; it != row[u.first].end() && *it <= u.second + k; it++) {
            if (*it > u.second) {
                res = dp1[u.first][*it] - (u.second == 0 ? 0 : dp1[u.first][u.second-1]);
            }
            else {
                res = dp1[u.first][u.second] - (*it == 0 ? 0 : dp1[u.first][*it-1]);
            }

            if (res != 0) {
                break;
            }

            dist[u.first][*it] = dist[u.first][u.second] + 1;
            q.push({u.first, *it});
            visited.push_back({u.first, *it});
        }
        target = max(0, u.first - k);
        p = col[u.second].lower_bound(target);
        for (auto it = p; it != col[u.second].end() && *it <= u.first + k; it++) {
            if (*it > u.first) {
                res = dp2[*it][u.second] - (u.first == 0 ? 0 : dp2[u.first-1][u.second]);
            }
            else {
                res = dp2[u.first][u.second] - (*it == 0 ? 0 : dp2[*it-1][u.second]);
            }

            if (res != 0) {
                break;
            }

            dist[*it][u.second] = dist[u.first][u.second] + 1;
            q.push({*it, u.second});
            visited.push_back({*it, u.second});
        }

        for (int i = 0; i < visited.size(); i++) {
            pair<int, int> v = visited[i];
            row[v.first].erase(v.second);
            col[v.second].erase(v.first);
        }
        visited.clear();
    }

    cout << dist[x2][y2] << '\n';

    return 0;
}

Compiler output:
a.cc:4:18: error: 'int y1' redeclared as different kind of entity
    4 | int h, w, k, x1, y1, x2, y2, res;
      |                  ^~
In file included from /usr/include/features.h:523,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/os_defines.h:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/c++config.h:683,
                 from /usr/include/c++/14/cassert:43,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:33,
                 from a.cc:1:
/usr/include/x86_64-linux-gnu/bits/mathcalls.h:257:1: note: previous declaration 'double y1(double)'
  257 | __MATHCALL (y1,, (_Mdouble_));
      | ^~~~~~~~~~
a.cc: In function 'int main()':
a.cc:15:30: error: no match for 'operator>>' (operand types are 'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} and 'double(double) noexcept')
   15 |     cin >> h >> w >> k >> x1 >> y1 >> x2 >> y2;
      |     ~~~~~~~~~~~~~~~~~~~~~~~~ ^~ ~~
      |                        |        |
      |                        |        double(double) noexcept
      |                        std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}
In file included from /usr/include/c++/14/sstream:40,
                 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/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:7: note:   conversion of argument 1 would be ill-formed:
a.cc:15:33: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'double (*)(double) noexcept'
   15 |     cin >> h >> w >> k >> x1 >> y1 >> x2 >> y2;
      |                                 ^~
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:7: note:   conversion of argument 1 would be ill-formed:
a.cc:15:33: error: invalid conversion from 'double (*)(double) noexcept' to 'short int' [-fpermissive]
   15 |     cin >> h >> w >> k >> x1 >> y1 >> x2 >> y2;
      |                                 ^~
      |                                 |
      |                                 double (*)(double) noexcept
a.cc:15:33: error: cannot bind rvalue '(short int)y1' to 'short int&'
/usr/include/c++/14/istream:177:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:7: note:   conversion of argument 1 would be ill-formed:
a.cc:15:33: error: invalid conversion from 'double (*)(double) noexcept' to 'short unsigned int' [-fpermissive]
   15 |     cin >> h >> w >> k >> x1 >> y1 >> x2 >> y2;
      |                                 ^~
      |                                 |
      |                                 double (*)(double) noexcept
a.cc:15:33: error: cannot bind rvalue '(short unsigned int)y1' to 'short unsigned int&'
/usr/include/c++/14/istream:181:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  181 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:181:7: note:   conversion of argument 1 would be ill-formed:
a.cc:15:33: error: invalid conversion from 'double (*)(double) noexcept' to 'int' [-fpermissive]
   15 |     cin >> h >> w >> k >> x1 >> y1 >> x2 >> y2;
      |                                 ^~
      |                                 |
      |                                 double (*)(double) noexcept
a.cc:15:33: error: cannot bind rvalue '(int)y1' to 'int&'
/usr/include/c++/14/istream:184:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:7: note:   conversion of argument 1 would be ill-formed:
a.cc:15:33: error: invalid conversion from 'double (*)(double) noexcept' to 'unsigned int' [-fpermissive]
   15 |     cin >> h >> w >> k >> x1 >> y1 >> x2 >> y2;
      |                                 ^~
      |                                 |
      |                                 double (*)(double) noexcept
a.cc:15:33: error: cannot bind rvalue '(unsigned int)y1' to 'unsigned int&'
/usr/include/c++/14/istream:188:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:7: note:   conversion of argument 1 would be ill-formed:
a.cc:15:33: error: invalid conversion from 'double (*)(double) noexcept' to 'long int' [-fpermissive]
   15 |     cin >> h >> w >> k >> x1 >> y1 >> x2 >> y2;
      |                                 ^~
      |                                 |
      |                                 double (*)(double) noexcept
a.cc:15:33: error: cannot bind rvalue '(long int)y1' to 'long int&'
/usr/include/c++/14/istream:192:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:7: note:   conversion of argument 1 would be ill-formed:
a.cc:15:33: error: invalid conversion from 'double (*)(double) noexcept' to 'long unsigned int' [-fpermissive]
   15 |     cin >> h >> w >> k >> x1 >> y1 >> x2 >> y2;
      |                                 ^~
      |                                 |
      |                                 double (*)(double) noexcept
a.cc:15:33: error: cannot bind rvalue '(long unsigned int)y1' to 'long unsigned int&'
/usr/include/c++/14/istream:199:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:7: note:   conversion of argument 1 would be ill-formed:
a.cc:15:33: error: invalid conversion from 'double (*)(double) noexcept' to 'long long int' [-fpermissive]
   15 |     cin >> h >> w >> k >> x1 >> y1 >> x2 >> y2;
      |                                 ^~
      |                                 |
      |                                 double (*)(double) noexcept
a.cc:15:33: error: cannot bind rvalue '(long long int)y1' to 'long long int&'
/usr/include/c++/14/istream:203:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:7: note:   conversion of argument 1 would be ill-formed:
a.cc:15:33: error: invalid conversion from 'double (*)(double) noexcept' to 'long long unsigned int' [-fpermissive]
   15 |     cin >> h >> w >> k >> x1 >> y1 >> x2 >> y2;
      |                                 ^~
      |                                 |
      |                                 double (*)(double) noexcept
a.cc:15:33: error: cannot bind rvalue '(long long unsigned int)y1' to 'long long unsigned int&'
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:7: note:   conversion of argument 1 would be ill-formed:
a.cc:15:33: error: invalid conversion from 'double (*)(double) noexcept' to 'void*' [-fpermissive]
   15 |     cin >> h >> w >> k >> x1 >> y1 >> x2 >> y2;
      |                                 ^~
      |                                 |
      |                                 double (*)(double) noexcept
a.cc:15:33: error: cannot bind rvalue '(void*)y1' to 'void*&'
/usr/include/c++/14/istream:122:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:122:7: note:   conversion of argument 1 would be ill-formed:
a.cc:15:33: error: invalid conversion from 'double (*)(double) noexcept' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'} [-fpermissive]
   15 |     cin >> h >> w >> k >> x1 >> y1 >> x2 >> y2;
      |                                 ^~
      |                                 |