Language: C++

#include <stack>
using namespace std;

int main(){
	stack<char> stk;
	string s;
	cin >> s;
	while(auto c: s){
		switch(c){
		case '0':
		case '1':
			stk.push(c);
		case 'B':
			if(!stk.empty()){
				stk.pop();
			}
		}
	}
	for(auto c: stk){
		cout >> c;
	}
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:6:9: error: 'string' was not declared in this scope
    6 |         string s;
      |         ^~~~~~
a.cc:2:1: note: 'std::string' is defined in header '<string>'; this is probably fixable by adding '#include <string>'
    1 | #include <stack>
  +++ |+#include <string>
    2 | using namespace std;
a.cc:7:9: error: 'cin' was not declared in this scope
    7 |         cin >> s;
      |         ^~~
a.cc:2:1: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
    1 | #include <stack>
  +++ |+#include <iostream>
    2 | using namespace std;
a.cc:7:16: error: 's' was not declared in this scope
    7 |         cin >> s;
      |                ^
a.cc:8:21: error: found ':' in nested-name-specifier, expected '::'
    8 |         while(auto c: s){
      |                     ^
      |                     ::
a.cc:8:20: error: 'c' has not been declared
    8 |         while(auto c: s){
      |                    ^
a.cc:8:24: error: qualified-id in declaration before ')' token
    8 |         while(auto c: s){
      |                        ^
a.cc:9:24: error: 'c' was not declared in this scope
    9 |                 switch(c){
      |                        ^
a.cc:19:21: error: no matching function for call to 'begin(std::stack<char>&)'
   19 |         for(auto c: stk){
      |                     ^~~
In file included from /usr/include/c++/14/bits/stl_deque.h:63,
                 from /usr/include/c++/14/deque:66,
                 from /usr/include/c++/14/stack:62,
                 from a.cc:1:
/usr/include/c++/14/initializer_list:88:5: note: candidate: 'template<class _Tp> constexpr const _Tp* std::begin(initializer_list<_Tp>)'
   88 |     begin(initializer_list<_Tp> __ils) noexcept
      |     ^~~~~
/usr/include/c++/14/initializer_list:88:5: note:   template argument deduction/substitution failed:
a.cc:19:21: note:   'std::stack<char>' is not derived from 'std::initializer_list<_Tp>'
   19 |         for(auto c: stk){
      |                     ^~~
In file included from /usr/include/c++/14/deque:68:
/usr/include/c++/14/bits/range_access.h:52:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.begin()) std::begin(_Container&)'
   52 |     begin(_Container& __cont) -> decltype(__cont.begin())
      |     ^~~~~
/usr/include/c++/14/bits/range_access.h:52:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/range_access.h: In substitution of 'template<class _Container> constexpr decltype (__cont.begin()) std::begin(_Container&) [with _Container = std::stack<char>]':
a.cc:19:14:   required from here
   19 |         for(auto c: stk){
      |                     ^~~
/usr/include/c++/14/bits/range_access.h:52:50: error: 'class std::stack<char>' has no member named 'begin'
   52 |     begin(_Container& __cont) -> decltype(__cont.begin())
      |                                           ~~~~~~~^~~~~
/usr/include/c++/14/bits/range_access.h:63:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.begin()) std::begin(const _Container&)'
   63 |     begin(const _Container& __cont) -> decltype(__cont.begin())
      |     ^~~~~
/usr/include/c++/14/bits/range_access.h:63:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/range_access.h: In substitution of 'template<class _Container> constexpr decltype (__cont.begin()) std::begin(const _Container&) [with _Container = std::stack<char>]':
a.cc:19:14:   required from here
   19 |         for(auto c: stk){
      |                     ^~~
/usr/include/c++/14/bits/range_access.h:63:56: error: 'const class std::stack<char>' has no member named 'begin'
   63 |     begin(const _Container& __cont) -> decltype(__cont.begin())
      |                                                 ~~~~~~~^~~~~
/usr/include/c++/14/bits/range_access.h:95:5: note: candidate: 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::begin(_Tp (&)[_Nm])'
   95 |     begin(_Tp (&__arr)[_Nm]) noexcept
      |     ^~~~~
/usr/include/c++/14/bits/range_access.h:95:5: note:   template argument deduction/substitution failed:
a.cc:19:21: note:   mismatched types '_Tp [_Nm]' and 'std::stack<char>'
   19 |         for(auto c: stk){
      |                     ^~~
/usr/include/c++/14/bits/range_access.h:113:31: note: candidate: 'template<class _Tp> _Tp* std::begin(valarray<_Tp>&)'
  113 |   template<typename _Tp> _Tp* begin(valarray<_Tp>&) noexcept;
      |                               ^~~~~
/usr/include/c++/14/bits/range_access.h:113:31: note:   template argument deduction/substitution failed:
a.cc:19:21: note:   'std::stack<char>' is not derived from 'std::valarray<_Tp>'
   19 |         for(auto c: stk){
      |                     ^~~
/usr/include/c++/14/bits/range_access.h:114:37: note: candidate: 'template<class _Tp> const _Tp* std::begin(const valarray<_Tp>&)'
  114 |   template<typename _Tp> const _Tp* begin(const valarray<_Tp>&) noexcept;
      |                                     ^~~~~
/usr/include/c++/14/bits/range_access.h:114:37: note:   template argument deduction/substitution failed:
a.cc:19:21: note:   'std::stack<char>' is not derived from 'const std::valarray<_Tp>'
   19 |         for(auto c: stk){
      |                     ^~~
a.cc:19:21: error: no matching function for call to 'end(std::stack<char>&)'
/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:   template argument deduction/substitution failed:
a.cc:19:21: note:   'std::stack<char>' is not derived from 'std::initializer_list<_Tp>'
   19 |         for(auto c: stk){
      |                     ^~~
/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:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/range_access.h: In substitution of 'template<class _Container> constexpr decltype (__cont.end()) std::end(_Container&) [with _Container = std::stack<char>]':
a.cc:19:14:   required from here
   19 |         for(auto c: stk){
      |                     ^~~
/usr/include/c++/14/bits/range_access.h:74:48: error: 'class std::stack<char>' has no member named 'end'
   74 |     end(_Container& __cont) -> decltype(__cont.end())
      |                                         ~~~~~~~^~~
/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:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/range_access.h: In substitution of 'template<class _Container> constexpr decltype (__cont.end()) std::end(const _Container&) [with _Container = std::stack<char>]':
a.cc:19:14:   required from here
   19 |         for(auto c: stk){
      |                     ^~~
/usr/include/c++/14/bits/range_access.h:85:54: error: 'const class std::stack<char>' has no member named 'end'
   85 |     end(const _Container& __cont) -> decltype(__cont.end())
      |                                               ~~~~~~~^~~
/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:   template argument deduction/substitution failed:
a.cc:19:21: note:   mismatched types '_Tp [_Nm]' and 'std::stack<char>'
   19 |         for(auto c: stk){
      |                     ^~~
/usr/include/c++/14/bits/range_access.h:115:31: note: candidate: 'template<class _Tp> _Tp* std::end(valarray<_Tp>&)'
  115 |   template<typename _Tp> _Tp* end(valarray<_Tp>&) noexcept;
      |                               ^~~
/usr/include/c++/14/bits/range_access.h:115:31: note:   template argument deduction/substitution failed:
a.cc:19:21: note:   'std::stack<char>' is not derived from 'std::valarray<_Tp>'
   19 |         for(auto c: stk){
      |                     ^~~
/usr/include/c++/14/bits/range_access.h:116:37: note: candidate: 'template<class _Tp> const _Tp* std::end(const valarray<_Tp>&)'
  116 |   template<typename _Tp> const _Tp* end(const valarray<_Tp>&) noexcept;
      |                                     ^~~
/usr/include/c++/14/bits/range_access.h:116:37: note:   template argument deduction/substitution failed:
a.cc:19:21: note:   'std::stack<char>' is not derived from 'const std::valarray<_Tp>'
   19 |         for(auto c: stk){
      |                     ^~~
a.cc:20:17: error: 'cout' was not declared in this scope
   20 |                 cout >> c;
      |                 ^~~~
a.cc:20:17: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'