Language: C++

#include<bits/stdc++.h>
using namespace std;
#define M 1000000000
int h,w,cnt;
char c[52][52];
vector<vector<int>> a(52,vector<int>(52,M));
int dx[4]={1,-1,0,0},dy[4]={0,0,1,-1};
queue<pair<int,int>> q;
bfs(int i,int j){
  for(int k=0;k<4;k++){
    if(c[i+dx[k]][j+[dy[k]]=='.'){
      if(a[i][j]+1<a[i+dx[k]][j+[dy[k]]){
        a[i+dx[k]][j+[dy[k]]=a[i][j]+1;
        q.push(make_pair(i+dx[k],j+dy[k]));
      }
    }
  }
}
int main(){
  cin>>h>>w;
  for(int i=1;i<=h;i++){
    for(int j=1;j<=w;j++){
      cin>>c[i][j];
      if(c[i][j]=='#'){
        cnt++;
      }
    }
  }
  a[1][1]=1;
  bfs(1,1);
  while(!q.empty()){
    bfs(q.front().first,q.front().second);
    q.pop();
  }
  if(a[h][w]==M)cout<<-1;
  else cout<<h*w-a[h][w]-cnt;
}

Compiler output:
a.cc:9:1: error: ISO C++ forbids declaration of 'bfs' with no type [-fpermissive]
    9 | bfs(int i,int j){
      | ^~~
a.cc: In function 'int bfs(int, int)':
a.cc:11:22: warning: capture of variable 'dy' with non-automatic storage duration
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                      ^~
a.cc:7:22: note: 'int dy [4]' declared here
    7 | int dx[4]={1,-1,0,0},dy[4]={0,0,1,-1};
      |                      ^~
a.cc:11:24: error: expected ',' before '[' token
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                        ^
      |                        ,
a.cc:11:24: error: expected identifier before '[' token
a.cc: In lambda function:
a.cc:11:28: error: expected '{' before '==' token
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                            ^~
a.cc: In function 'int bfs(int, int)':
a.cc:11:20: error: no match for 'operator+' (operand types are 'int' and 'bfs(int, int)::<lambda()>')
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                   ~^~~~~~~~
      |                   | |
      |                   | bfs(int, int)::<lambda()>
      |                   int
In file included from /usr/include/c++/14/bits/stl_algobase.h:67,
                 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/stl_iterator.h:627:5: note: candidate: 'template<class _Iterator> constexpr std::reverse_iterator<_Iterator> std::operator+(typename reverse_iterator<_Iterator>::difference_type, const reverse_iterator<_Iterator>&)'
  627 |     operator+(typename reverse_iterator<_Iterator>::difference_type __n,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:627:5: note:   template argument deduction/substitution failed:
a.cc:11:28: note:   'bfs(int, int)::<lambda()>' is not derived from 'const std::reverse_iterator<_Iterator>'
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                            ^~
/usr/include/c++/14/bits/stl_iterator.h:1798:5: note: candidate: 'template<class _Iterator> constexpr std::move_iterator<_IteratorL> std::operator+(typename move_iterator<_IteratorL>::difference_type, const move_iterator<_IteratorL>&)'
 1798 |     operator+(typename move_iterator<_Iterator>::difference_type __n,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1798:5: note:   template argument deduction/substitution failed:
a.cc:11:28: note:   'bfs(int, int)::<lambda()>' is not derived from 'const std::move_iterator<_IteratorL>'
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                            ^~
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:
/usr/include/c++/14/bits/basic_string.h:3598:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3598 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3598:5: note:   template argument deduction/substitution failed:
a.cc:11:28: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'int'
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                            ^~
/usr/include/c++/14/bits/basic_string.h:3616:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3616 |     operator+(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3616:5: note:   template argument deduction/substitution failed:
a.cc:11:28: note:   mismatched types 'const _CharT*' and 'int'
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                            ^~
/usr/include/c++/14/bits/basic_string.h:3635:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(_CharT, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3635 |     operator+(_CharT __lhs, const basic_string<_CharT,_Traits,_Alloc>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3635:5: note:   template argument deduction/substitution failed:
a.cc:11:28: note:   'bfs(int, int)::<lambda()>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                            ^~
/usr/include/c++/14/bits/basic_string.h:3652:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3652 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3652:5: note:   template argument deduction/substitution failed:
a.cc:11:28: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'int'
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                            ^~
/usr/include/c++/14/bits/basic_string.h:3670:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, _CharT)'
 3670 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs, _CharT __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3670:5: note:   template argument deduction/substitution failed:
a.cc:11:28: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'int'
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                            ^~
/usr/include/c++/14/bits/basic_string.h:3682:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3682 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3682:5: note:   template argument deduction/substitution failed:
a.cc:11:28: note:   mismatched types 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'int'
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                            ^~
/usr/include/c++/14/bits/basic_string.h:3689:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3689 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3689:5: note:   template argument deduction/substitution failed:
a.cc:11:28: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'int'
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                            ^~
/usr/include/c++/14/bits/basic_string.h:3696:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3696 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3696:5: note:   template argument deduction/substitution failed:
a.cc:11:28: note:   mismatched types 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'int'
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                            ^~
/usr/include/c++/14/bits/basic_string.h:3719:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const _CharT*, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3719 |     operator+(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3719:5: note:   template argument deduction/substitution failed:
a.cc:11:28: note:   mismatched types 'const _CharT*' and 'int'
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                            ^~
/usr/include/c++/14/bits/basic_string.h:3726:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(_CharT, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3726 |     operator+(_CharT __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3726:5: note:   template argument deduction/substitution failed:
a.cc:11:28: note:   'bfs(int, int)::<lambda()>' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                            ^~
/usr/include/c++/14/bits/basic_string.h:3733:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, const _CharT*)'
 3733 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3733:5: note:   template argument deduction/substitution failed:
a.cc:11:28: note:   mismatched types 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'int'
   11 |     if(c[i+dx[k]][j+[dy[k]]=='.'){
      |                            ^~
/usr/include/c++/14/bits/basic_string.h:3740:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, _CharT)'