Language: C++

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

int main() {
  int h, w;
  cin >> h >> w;
  vector<char> vec(h+2,vector<char>(w+2));
  for(int i = 1; i < h+1;i++){
  for(int j = 1; j < w+1;j++){
  cin >>vec.at(i).at(j);
  }
  }
  for(int i = 0; i < w + 2;i++){
  vec.at(0).at(i) = '#';
  vec.at(h+1).at(i) = '#';
  }
  for(int i = 0; i < h + 2;i++){
  vec.at(i).at(0) = '#';
  vec.at(i).at(w+1) = '#';
  }
for(int i = 0; i < h+2;i++){
  for(int j = 0; j < w+2;j++){
  cout << vec.at(i).at(j);
  }
  cout << endl;
  }
}


Compiler output:
a.cc: In function 'int main()':
a.cc:7:41: error: no matching function for call to 'std::vector<char>::vector(int, std::vector<char>)'
    7 |   vector<char> vec(h+2,vector<char>(w+2));
      |                                         ^
In file included from /usr/include/c++/14/vector:66,
                 from /usr/include/c++/14/functional:64,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53,
                 from a.cc:1:
/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 = char; _Alloc = std::allocator<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:7:41: note:   deduced conflicting types for parameter '_InputIterator' ('int' and 'std::vector<char>')
    7 |   vector<char> vec(h+2,vector<char>(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 = char; _Alloc = std::allocator<char>; allocator_type = std::allocator<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<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 = char; _Alloc = std::allocator<char>; std::__type_identity_t<_Alloc> = std::allocator<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<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 = char; _Alloc = std::allocator<char>; allocator_type = std::allocator<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 = char; _Alloc = std::allocator<char>; allocator_type = std::allocator<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 = char; _Alloc = std::allocator<char>; std::__type_identity_t<_Alloc> = std::allocator<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<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 = char; _Alloc = std::allocator<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 = char; _Alloc = std::allocator<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 = char; _Alloc = std::allocator<char>; size_type = long unsigned int; value_type = char; allocator_type = std::allocator<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<char>' to 'const std::vector<char>::value_type&' {aka 'const 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 = char; _Alloc = std::allocator<char>; size_type = long unsigned int; allocator_type = std::allocator<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<char>' to 'const std::vector<char>::allocator_type&' {aka 'const std::allocator<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 = char; _Alloc = std::allocator<char>; allocator_type = std::allocator<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 = char; _Alloc = std::allocator<char>]'
  531 |       vector() = default;
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:531:7: note:   candidate expects 0 arguments, 2 provided
a.cc:10:19: error: request for member 'at' in 'vec.std::vector<char>::at(((std::vector<char>::size_type)i))', which is of non-class type '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'}
   10 |   cin >>vec.at(i).at(j);
      |                   ^~
a.cc:14:13: error: request for member 'at' in 'vec.std::vector<char>::at(0)', which is of non-class type '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'}
   14 |   vec.at(0).at(i) = '#';
      |             ^~
a.cc:15:15: error: request for member 'at' in 'vec.std::vector<char>::at(((std::vector<char>::size_type)(h + 1)))', which is of non-class type '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'}
   15 |   vec.at(h+1).at(i) = '#';
      |               ^~
a.cc:18:13: error: request for member 'at' in 'vec.std::vector<char>::at(((std::vector<char>::size_type)i))', which is of non-class type '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'}
   18 |   vec.at(i).at(0) = '#';
      |             ^~
a.cc:19:13: error: request for member 'at' in 'vec.std::vector<char>::at(((std::vector<char>::size_type)i))', which is of non-class type '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'}
   19 |   vec.at(i).at(w+1) = '#';
      |             ^~
a.cc:23:21: error: request for member 'at' in 'vec.std::vector<char>::at(((std::vector<char>::size_type)i))', which is of non-class type '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'}
   23 |   cout << vec.at(i).at(j);
      |                     ^~