Language: C++

#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")

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

#define pb push_back
#define F first
#define S second
#define f(i,a,b)  for(int i = a; i < b; i++)
//#define endl '\n'

using ll = long long;
using db = long double;
using ii = pair<int, int>;

const int N = 2e5 + 5, LG = 19, MOD = 998244353;
const int SQ =225;
const long double EPS = 1e-6;
vector<set<int>> row, col;
vector<set<int>> frow, fcol;
int h, w, k, x1, y1, x2, y2;
vector<vector<char>> grid;
vector<vector<int>> dist;
int32_t main(){
#ifdef ONLINE_JUDGE
    ios_base::sync_with_stdio(0);
    cin.tie(0);
#endif

  cin >> h >> w >> k;
  cin >> x1 >> y1 >> x2 >> y2;
  --x1,--x2,--y1,--y2;

  row.resize(h);
  col.resize(w);
  frow.resize(h);
  fcol.resize(w);

  grid.assign(h, vector<char>(w));
  dist.assign(h, vector<int>(w, -1));
  f(i,0,h)row[i].insert(-1e9), row[i].insert(1e9);
  f(i,0,w)col[i].insert(-1e9), col[i].insert(1e9);
  f(i,0,h)frow[i].insert(-1e9), frow[i].insert(1e9);
  f(i,0,w)fcol[i].insert(-1e9), fcol[i].insert(1e9);
  f(i,0,h)
    f(j,0,w){
      cin >> grid[i][j];
      if(grid[i][j] == '.'){
        row[i].insert(j);
        col[j].insert(i);
      } else {
        frow[i].insert(j);
        fcol[j].insert(i);
      }
    }

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

  while(q.size()){

    auto cur = q.front();
    q.pop();
//    cout << cur.F << ' ' << cur.S << ' ' << dist[cur.F][cur.S] << endl;
    ///move right;
    auto it = row[cur.F].upper_bound(cur.S);
    if(*frow[cur.F].upper_bound(cur.S) > *it)
    while(*it - cur.S <= k){
      auto nxt = next(it);
      bool f = (*frow[cur.F].upper_bound(*it)) < *nxt;
      q.push(ii(cur.F,*it));
      dist[cur.F][*it] = dist[cur.F][cur.S] + 1;
      col[*it].erase(cur.F);
      row[cur.F].erase(it);
      if(f)break;
      it = nxt;
    }

    ///move left;
    it = --row[cur.F].upper_bound(cur.S);
    if(*(--frow[cur.F].upper_bound(cur.S)) < *it)
    while(cur.S - *it <= k){
      auto nxt = prev(it);
      bool f = (*(--frow[cur.F].upper_bound(*it))) > *nxt;
      q.push(ii(cur.F,*it));
      dist[cur.F][*it] = dist[cur.F][cur.S] + 1;
      col[*it].erase(cur.F);
      row[cur.F].erase(it);
      if(f)break;
      it = nxt;
    }

    ///move down;
    it = col[cur.S].upper_bound(cur.F);
    if(*fcol[cur.S].upper_bound(cur.F) > *it)
    while(*it - cur.S <= k){
      auto nxt = next(it);
      bool f = (*fcol[cur.S].upper_bound(*it)) < *nxt;
      q.push(ii(*it, cur.S));
      dist[*it][cur.S] = dist[cur.F][cur.S] + 1;
      row[*it].erase(cur.S);
      col[cur.S].erase(it);
      if(f)break;
      it = nxt;
    }

    ///move up;
    it = --col[cur.S].upper_bound(cur.F);
    if(*(--fcol[cur.S].upper_bound(cur.F)) < *it)
    while(cur.S - *it <= k){
      auto nxt = prev(it);
      bool f = (*(--fcol[cur.S].upper_bound(*it))) > *nxt;
      q.push(ii(*it, cur.S));
      dist[*it][cur.S] = dist[cur.F][cur.S] + 1;
      row[*it].erase(cur.S);
      col[cur.S].erase(it);
      if(f)break;
      it = nxt;
    }


  }

  cout << dist[x2][y2] << endl;

  return 0;
}


Compiler output:
a.cc:22:18: error: 'int y1' redeclared as different kind of entity
   22 | int h, w, k, x1, y1, x2, y2;
      |                  ^~
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:4:
/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 'int32_t main()':
a.cc:32:13: error: no match for 'operator>>' (operand types are 'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} and 'double(double) noexcept')
   32 |   cin >> 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:32:16: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'double (*)(double) noexcept'
   32 |   cin >> 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:32:16: error: invalid conversion from 'double (*)(double) noexcept' to 'short int' [-fpermissive]
   32 |   cin >> x1 >> y1 >> x2 >> y2;
      |                ^~
      |                |
      |                double (*)(double) noexcept
a.cc:32:16: 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:32:16: error: invalid conversion from 'double (*)(double) noexcept' to 'short unsigned int' [-fpermissive]
   32 |   cin >> x1 >> y1 >> x2 >> y2;
      |                ^~
      |                |
      |                double (*)(double) noexcept
a.cc:32:16: 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:32:16: error: invalid conversion from 'double (*)(double) noexcept' to 'int' [-fpermissive]
   32 |   cin >> x1 >> y1 >> x2 >> y2;
      |                ^~
      |                |
      |                double (*)(double) noexcept
a.cc:32:16: 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:32:16: error: invalid conversion from 'double (*)(double) noexcept' to 'unsigned int' [-fpermissive]
   32 |   cin >> x1 >> y1 >> x2 >> y2;
      |                ^~
      |                |
      |                double (*)(double) noexcept
a.cc:32:16: 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:32:16: error: invalid conversion from 'double (*)(double) noexcept' to 'long int' [-fpermissive]
   32 |   cin >> x1 >> y1 >> x2 >> y2;
      |                ^~
      |                |
      |                double (*)(double) noexcept
a.cc:32:16: 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:32:16: error: invalid conversion from 'double (*)(double) noexcept' to 'long unsigned int' [-fpermissive]
   32 |   cin >> x1 >> y1 >> x2 >> y2;
      |                ^~
      |                |
      |                double (*)(double) noexcept
a.cc:32:16: 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:32:16: error: invalid conversion from 'double (*)(double) noexcept' to 'long long int' [-fpermissive]
   32 |   cin >> x1 >> y1 >> x2 >> y2;
      |                ^~
      |                |
      |                double (*)(double) noexcept
a.cc:32:16: 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:32:16: error: invalid conversion from 'double (*)(double) noexcept' to 'long long unsigned int' [-fpermissive]
   32 |   cin >> x1 >> y1 >> x2 >> y2;
      |                ^~
      |                |
      |                double (*)(double) noexcept
a.cc:32:16: 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:32:16: error: invalid conversion from 'double (*)(double) noexcept' to 'void*' [-fpermissive]
   32 |   cin >> x1 >> y1 >> x2 >> y2;
      |                ^~
      |                |
      |                double (*)(double) noexcept
a.cc:32:16: 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:32:16: 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]
   32 |   cin >> x1 >> y1 >> x2 >> y2;
      |                ^~
      |                |
      |                double (*)(double) noexcept
/usr/include/c++/14/istream:126:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__ios_type& (*)(__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>; __ios_type = std::basic_ios<char>]' (near match)
  126 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:126:7: note:   conversion of argument 1 would be ill-formed:
a.cc:32:16: error: invalid conversion from 'double (*)(double) noexcept' to 'std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&)' {aka 'std::basic_ios<char>& (*)(std::basic_ios<char>&)'} [-fpermissiv