Language: C++

#include <iostream>
#include <vector>
using namespace std;

int main(){
  int h, w;
  cin >> h >> w;
  vector<vector<char>>a(h+2, vector<int>(w+2, '.'));
  for(int i=1; i<=h; i++)for(int j=1; j<=w; j++)cin >> a[i][j];
  int x=1, y=1;
  for(int i=0; i<2n; i++){#include <iostream>
#include <vector>
using namespace std;

int main(){
  int h, w;
  cin >> h >> w;
  vector<vector<bool>>chk(h+2, vector<bool>(w+2, false));
  vector<vector<char>>a(h+2, vector<char>(w+2, '.'));
  for(int i=1; i<=h; i++)for(int j=1; j<=w; j++)cin >> a[i][j];
  int x=1, y=1;
  chk[x][y]=true;
  for(int i=0; i<h+w; i++){
    if(i%2==0)while(a[x+1][y]=='#'){x++; chk[x][y]=true;}
    if(i%2==0)while(a[x][y+1]=='#'){y++; chk[x][y]=true;}
  }
  if(!(x==h && y==w)){cout << "Impossible"; return 0;}
  for(int i=1; i<=h; i++)for(int j=1; j<=w; j++)if(a[i][j]=='#' && (!chk[i][j])){cout << "Impossible"; return 0;}
  cout << "Possible";
  return 0;
}
    if(i%2==0)while(a[x+1][y]=='#')x++;
    if(i%2==0)while(a[x][y+1]=='#')y++;
  }
  if(x==n && y==n)cout << "Possible";
  else cout << "Impossible";
}

Compiler output:
a.cc:11:27: error: stray '#' in program
   11 |   for(int i=0; i<2n; i++){#include <iostream>
      |                           ^
a.cc: In function 'int main()':
a.cc:8:51: error: no matching function for call to 'std::vector<std::vector<char> >::vector(int, std::vector<int>)'
    8 |   vector<vector<char>>a(h+2, vector<int>(w+2, '.'));
      |                                                   ^
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:2:
/usr/include/c++/14/bits/stl_vector.h:707:9: note: candidate: 'template<class _InputIterator, class> std::vector<_Tp, _Alloc>::vector(_InputIterator, _InputIterator, const allocator_type&) [with <template-parameter-2-2> = _InputIterator; _Tp = std::vector<char>; _Alloc = std::allocator<std::vector<char> >]'
  707 |         vector(_InputIterator __first, _InputIterator __last,
      |         ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:707:9: note:   template argument deduction/substitution failed:
a.cc:8:51: note:   deduced conflicting types for parameter '_InputIterator' ('int' and 'std::vector<int>')
    8 |   vector<vector<char>>a(h+2, vector<int>(w+2, '.'));
      |                                                   ^
/usr/include/c++/14/bits/stl_vector.h:678:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::initializer_list<_Tp>, const allocator_type&) [with _Tp = std::vector<char>; _Alloc = std::allocator<std::vector<char> >; allocator_type = std::allocator<std::vector<char> >]'
  678 |       vector(initializer_list<value_type> __l,
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:678:43: note:   no known conversion for argument 1 from 'int' to 'std::initializer_list<std::vector<char> >'
  678 |       vector(initializer_list<value_type> __l,
      |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:659:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&, std::__type_identity_t<_Alloc>&) [with _Tp = std::vector<char>; _Alloc = std::allocator<std::vector<char> >; std::__type_identity_t<_Alloc> = std::allocator<std::vector<char> >]'
  659 |       vector(vector&& __rv, const __type_identity_t<allocator_type>& __m)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:659:23: note:   no known conversion for argument 1 from 'int' to 'std::vector<std::vector<char> >&&'
  659 |       vector(vector&& __rv, const __type_identity_t<allocator_type>& __m)
      |              ~~~~~~~~~^~~~
/usr/include/c++/14/bits/stl_vector.h:640:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&, const allocator_type&, std::false_type) [with _Tp = std::vector<char>; _Alloc = std::allocator<std::vector<char> >; allocator_type = std::allocator<std::vector<char> >; std::false_type = std::false_type]'
  640 |       vector(vector&& __rv, const allocator_type& __m, false_type)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:640:7: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/stl_vector.h:635:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&, const allocator_type&, std::true_type) [with _Tp = std::vector<char>; _Alloc = std::allocator<std::vector<char> >; allocator_type = std::allocator<std::vector<char> >; std::true_type = std::true_type]'
  635 |       vector(vector&& __rv, const allocator_type& __m, true_type) noexcept
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:635:7: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/stl_vector.h:624:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&, std::__type_identity_t<_Alloc>&) [with _Tp = std::vector<char>; _Alloc = std::allocator<std::vector<char> >; std::__type_identity_t<_Alloc> = std::allocator<std::vector<char> >]'
  624 |       vector(const vector& __x, const __type_identity_t<allocator_type>& __a)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:624:28: note:   no known conversion for argument 1 from 'int' to 'const std::vector<std::vector<char> >&'
  624 |       vector(const vector& __x, const __type_identity_t<allocator_type>& __a)
      |              ~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:620:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&) [with _Tp = std::vector<char>; _Alloc = std::allocator<std::vector<char> >]'
  620 |       vector(vector&&) noexcept = default;
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:620:7: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_vector.h:601:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&) [with _Tp = std::vector<char>; _Alloc = std::allocator<std::vector<char> >]'
  601 |       vector(const vector& __x)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:601:7: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_vector.h:569:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(size_type, const value_type&, const allocator_type&) [with _Tp = std::vector<char>; _Alloc = std::allocator<std::vector<char> >; size_type = long unsigned int; value_type = std::vector<char>; allocator_type = std::allocator<std::vector<char> >]'
  569 |       vector(size_type __n, const value_type& __value,
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:569:47: note:   no known conversion for argument 2 from 'std::vector<int>' to 'const std::vector<std::vector<char> >::value_type&' {aka 'const std::vector<char>&'}
  569 |       vector(size_type __n, const value_type& __value,
      |                             ~~~~~~~~~~~~~~~~~~^~~~~~~
/usr/include/c++/14/bits/stl_vector.h:556:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(size_type, const allocator_type&) [with _Tp = std::vector<char>; _Alloc = std::allocator<std::vector<char> >; size_type = long unsigned int; allocator_type = std::allocator<std::vector<char> >]'
  556 |       vector(size_type __n, const allocator_type& __a = allocator_type())
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:556:51: note:   no known conversion for argument 2 from 'std::vector<int>' to 'const std::vector<std::vector<char> >::allocator_type&' {aka 'const std::allocator<std::vector<char> >&'}
  556 |       vector(size_type __n, const allocator_type& __a = allocator_type())
      |                             ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:542:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(const allocator_type&) [with _Tp = std::vector<char>; _Alloc = std::allocator<std::vector<char> >; allocator_type = std::allocator<std::vector<char> >]'
  542 |       vector(const allocator_type& __a) _GLIBCXX_NOEXCEPT
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:542:7: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_vector.h:531:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector() [with _Tp = std::vector<char>; _Alloc = std::allocator<std::vector<char> >]'
  531 |       vector() = default;
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:531:7: note:   candidate expects 0 arguments, 2 provided
a.cc:11:18: error: unable to find numeric literal operator 'operator""n'
   11 |   for(int i=0; i<2n; i++){#include <iostream>
      |                  ^~
a.cc:11:28: error: 'include' was not declared in this scope
   11 |   for(int i=0; i<2n; i++){#include <iostream>
      |                            ^~~~~~~
a.cc:11:45: error: expected primary-expression before '>' token
   11 |   for(int i=0; i<2n; i++){#include <iostream>
      |                                             ^
a.cc:13:1: error: expected primary-expression before 'using'
   13 | using namespace std;
      | ^~~~~
a.cc:15:9: warning: empty parentheses were disambiguated as a function declaration [-Wvexing-parse]
   15 | int main(){
      |         ^~
a.cc:15:9: note: remove parentheses to default-initialize a variable
   15 | int main(){
      |         ^~
      |         --
a.cc:15:9: note: or replace parentheses with braces to value-initialize a variable
a.cc:15:11: error: a function-definition is not allowed here before '{' token
   15 | int main(){
      |           ^
a.cc:35:9: error: 'n' was not declared in this scope
   35 |   if(x==n && y==n)cout << "Possible";
      |         ^