Language: C++

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

struct Card{
	char a;
	int b;
};

bool compare_as_ints(Card i, Card j){
	return(i.b<j.b);
};

int partition(Card A[],int p,int r){
	Card x=A[r];
	int i=p-1;
	for(int j=p;j=r-1;j++){
		if(A[j].b<=x.b){
			i++;
			swap(A[i],A[j]);
		}
	}
	swap(A[i+1],A[r]);
	return i+1;
}

void quicksort(Card A[],int p,int r){
	if(p<r){
		int q=partition(A,p,r);
		quicksort(A,p,q-1);
		quicksort(A,q+1,r);
	}
}

int main(){
	int n;
	cin>>n;
	Card A[100000],B[100000];
	for (int i=0;i<n;i++){
		cin>>A[i].a>>A[i].b;
		B[i]=A[i];
	}

	quicksort(A,0,n-1);
	stable_sort(B,B+n,compare_as_ints);

	//
	int t=0;//????????????????????°?¶?????????°
	for(int i=0;i<n;i++){
		if(A[i]!=B[i]){
			t++;
		}
	}
	if(t==0){
		cout<<"Stable"<<endl;
	}else{
		cout<<"Not"<<' '<<"stable"<<endl;
	}
	//
	for(int i=0;i<n;i++){
		cout<<A[i].a<< ' '<<A[i].b<<endl;
	}
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:50:24: error: no match for 'operator!=' (operand types are 'Card' and 'Card')
   50 |                 if(A[i]!=B[i]){
      |                    ~~~~^~~~~~
      |                       |     |
      |                       Card  Card
In file included from /usr/include/c++/14/iosfwd:42,
                 from /usr/include/c++/14/ios:40,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/postypes.h:197:5: note: candidate: 'template<class _StateT> bool std::operator!=(const fpos<_StateT>&, const fpos<_StateT>&)'
  197 |     operator!=(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/postypes.h:197:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   'Card' is not derived from 'const std::fpos<_StateT>'
   50 |                 if(A[i]!=B[i]){
      |                             ^
In file included from /usr/include/c++/14/string:43,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44:
/usr/include/c++/14/bits/allocator.h:243:5: note: candidate: 'template<class _T1, class _T2> bool std::operator!=(const allocator<_CharT>&, const allocator<_T2>&)'
  243 |     operator!=(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/14/bits/allocator.h:243:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   'Card' is not derived from 'const std::allocator<_CharT>'
   50 |                 if(A[i]!=B[i]){
      |                             ^
In file included from /usr/include/c++/14/string:48:
/usr/include/c++/14/bits/stl_iterator.h:455:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator!=(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  455 |     operator!=(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:455:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   'Card' is not derived from 'const std::reverse_iterator<_Iterator>'
   50 |                 if(A[i]!=B[i]){
      |                             ^
/usr/include/c++/14/bits/stl_iterator.h:500:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator!=(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  500 |     operator!=(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:500:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   'Card' is not derived from 'const std::reverse_iterator<_Iterator>'
   50 |                 if(A[i]!=B[i]){
      |                             ^
/usr/include/c++/14/bits/stl_iterator.h:1686:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator!=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1686 |     operator!=(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1686:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   'Card' is not derived from 'const std::move_iterator<_IteratorL>'
   50 |                 if(A[i]!=B[i]){
      |                             ^
/usr/include/c++/14/bits/stl_iterator.h:1753:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator!=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1753 |     operator!=(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1753:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   'Card' is not derived from 'const std::move_iterator<_IteratorL>'
   50 |                 if(A[i]!=B[i]){
      |                             ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/string:51:
/usr/include/c++/14/bits/stl_pair.h:1052:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator!=(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1052 |     operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1052:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   'Card' is not derived from 'const std::pair<_T1, _T2>'
   50 |                 if(A[i]!=B[i]){
      |                             ^
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54:
/usr/include/c++/14/string_view:651:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator!=(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  651 |     operator!=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:651:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   'Card' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   50 |                 if(A[i]!=B[i]){
      |                             ^
/usr/include/c++/14/string_view:658:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator!=(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  658 |     operator!=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:658:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   'Card' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   50 |                 if(A[i]!=B[i]){
      |                             ^
/usr/include/c++/14/string_view:666:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator!=(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  666 |     operator!=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:666:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   'Card' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   50 |                 if(A[i]!=B[i]){
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3833:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator!=(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3833 |     operator!=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3833:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   'Card' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   50 |                 if(A[i]!=B[i]){
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3847:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator!=(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3847 |     operator!=(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3847:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   mismatched types 'const _CharT*' and 'Card'
   50 |                 if(A[i]!=B[i]){
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3860:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator!=(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3860 |     operator!=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3860:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   'Card' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   50 |                 if(A[i]!=B[i]){
      |                             ^
In file included from /usr/include/c++/14/bits/memory_resource.h:47,
                 from /usr/include/c++/14/string:68:
/usr/include/c++/14/tuple:2613:5: note: candidate: 'template<class ... _TElements, class ... _UElements> constexpr bool std::operator!=(const tuple<_UTypes ...>&, const tuple<_Elements ...>&)'
 2613 |     operator!=(const tuple<_TElements...>& __t,
      |     ^~~~~~~~
/usr/include/c++/14/tuple:2613:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   'Card' is not derived from 'const std::tuple<_UTypes ...>'
   50 |                 if(A[i]!=B[i]){
      |                             ^
In file included from /usr/include/c++/14/bits/locale_facets.h:48,
                 from /usr/include/c++/14/bits/basic_ios.h:37,
                 from /usr/include/c++/14/ios:46:
/usr/include/c++/14/bits/streambuf_iterator.h:242:5: note: candidate: 'template<class _CharT, class _Traits> bool std::operator!=(const istreambuf_iterator<_CharT, _Traits>&, const istreambuf_iterator<_CharT, _Traits>&)'
  242 |     operator!=(const istreambuf_iterator<_CharT, _Traits>& __a,
      |     ^~~~~~~~
/usr/include/c++/14/bits/streambuf_iterator.h:242:5: note:   template argument deduction/substitution failed:
a.cc:50:29: note:   'Card' is not derived from 'const std::istreambuf_iterator<_CharT, _Traits>'
   50 |                 if(A[i]!=B[i]){
      |                             ^
In file included from /usr/include/c++/14/bits/ios_base.h:46:
/usr/include/c++/14/system_error:525:3: note: candidate: 'bool std::operator!=(const error_code&, const error_code&)'
  525 |   operator!=(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/14/system_error:525:32: note:   no known conversion for argument 1 from 'Card' to 'const std::error_code&'
  525 |   operator!=(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/14/s