Language: C++

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

int main(){
  int n;
  cin >> n;
  vector<int> b;
  for(int i=0;i<n;i++){
    char a;
    cin >> a;
    if(i%2) b.push_back(a);
    else b.pop_back(a);
  }
  if(n%2) reverse(b.begin(),b,end());
  for(int i=0;i<n-1;i++) cout << b.at(i) << " ";
  cout << b.at(n-1) << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:12:20: error: no matching function for call to 'std::vector<int>::pop_back(char&)'
   12 |     else b.pop_back(a);
      |          ~~~~~~~~~~^~~
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:1324:7: note: candidate: 'void std::vector<_Tp, _Alloc>::pop_back() [with _Tp = int; _Alloc = std::allocator<int>]'
 1324 |       pop_back() _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1324:7: note:   candidate expects 0 arguments, 1 provided
a.cc:14:34: error: no matching function for call to 'end()'
   14 |   if(n%2) reverse(b.begin(),b,end());
      |                               ~~~^~
In file included from /usr/include/c++/14/bits/algorithmfwd.h:39,
                 from /usr/include/c++/14/bits/stl_algo.h:59,
                 from /usr/include/c++/14/algorithm:61,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/initializer_list:99:5: note: candidate: 'template<class _Tp> constexpr const _Tp* std::end(initializer_list<_Tp>)'
   99 |     end(initializer_list<_Tp> __ils) noexcept
      |     ^~~
/usr/include/c++/14/initializer_list:99:5: note:   candidate expects 1 argument, 0 provided
In file included from /usr/include/c++/14/string:53,
                 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/range_access.h:74:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.end()) std::end(_Container&)'
   74 |     end(_Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:74:5: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/range_access.h:85:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.end()) std::end(const _Container&)'
   85 |     end(const _Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:85:5: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/range_access.h:106:5: note: candidate: 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::end(_Tp (&)[_Nm])'
  106 |     end(_Tp (&__arr)[_Nm]) noexcept
      |     ^~~
/usr/include/c++/14/bits/range_access.h:106:5: note:   candidate expects 1 argument, 0 provided
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166:
/usr/include/c++/14/valarray:1249:5: note: candidate: 'template<class _Tp> _Tp* std::end(valarray<_Tp>&)'
 1249 |     end(valarray<_Tp>& __va) noexcept
      |     ^~~
/usr/include/c++/14/valarray:1249:5: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/valarray:1265:5: note: candidate: 'template<class _Tp> const _Tp* std::end(const valarray<_Tp>&)'
 1265 |     end(const valarray<_Tp>& __va) noexcept
      |     ^~~
/usr/include/c++/14/valarray:1265:5: note:   candidate expects 1 argument, 0 provided