Language: C++

#include <iostream>
#include <vector>
#include <algorithm>
#include <climits>
#include <string>
#define rep(i,a) for(i=0;i<a;i++)
using namespace std;

struct card{
    char mark;
    int num;
};
 
int partition(vector<card> &qs, int p, int r) {
    int i,j,x;
    x = qs[r].num;
    i = p-1;
 
    for(j=p; j <= r-1; j++) {
        if(qs[j].num <= x){
            i = i+1;
            swap(qs[i],qs[j]);
        }
    }
    swap(qs[i+1],qs[r]);
    return i+1;
}

void quicksort(vector<card> &qs, int p, int r) {
    if(p < r) {
        int q = partition(qs,p,r);
        quicksort(qs, p, q-1);
        quicksort(qs, q+1, r);
    }
}

void merge(vector<card> &ms, int l, int m, int r){
    int n1 = m-l;
    int n2 = r-m;
    int i,j;
    vector<card> L(n1+1);
    vector<card> R(n2+2);
    rep(i,n1){
        L[i] = ms[l+i];
    }
    rep(i,n2) {
        R[i] = ms[m+i];
    }
    L[n1].num = INT_MAX;
    R[n2].num = INT_MAX;
    i = 0;
    j = 0;
    for(int k = l; k < r; k++) {
        if(L[i].num <= R[j].num) {
            ms[k] = L[i];
            i++;
        } else if(ms[k].num = R[j].num) {
            j++;
        }
    }
}

void mergesort(vector<card> &ms, int l, int r) {
    if (l+1 < r) {
        int m = (l+r)/2;
        mergesort(ms,l,m);
        mergesort(ms,m,r);
        merge(ms,l,m,r);
    }
}

bool check(vector<card> &qs, vector<card> &ms)
{
    int i;
    rep(i,n){
        if(qs[i] != ms[i]){
            return false;
        }
    }
    return true;
}
 
int main(void) {
    int n,i;
    card c1;
    vector<card> qs;
     
    cin >> n;
    rep(i,n) {
        cin >> c1.mark >> c1.num;
        qs.push_back(c1);
    }
    vector<card> ms(qs.begin(),qs.end());

    quicksort(qs,0,n-1);
    mergesort(ms,0,n);

    if(check(qs,ms)) {
        cout << "Stable" << endl;
    } else {
        cout << "Not Stable" << endl;
    }

    rep(i,n) {
        cout << qs[i] << endl;
    }
    return 0;
}

Compiler output:
a.cc: In function 'bool check(std::vector<card>&, std::vector<card>&)':
a.cc:75:11: error: 'n' was not declared in this scope
   75 |     rep(i,n){
      |           ^
a.cc:6:28: note: in definition of macro 'rep'
    6 | #define rep(i,a) for(i=0;i<a;i++)
      |                            ^
a.cc:76:18: error: no match for 'operator!=' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<card>, card>::value_type' {aka 'card'} and '__gnu_cxx::__alloc_traits<std::allocator<card>, card>::value_type' {aka 'card'})
   76 |         if(qs[i] != ms[i]){
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:76:25: note:   '__gnu_cxx::__alloc_traits<std::allocator<card>, card>::value_type' {aka 'card'} is not derived from 'const std::fpos<_StateT>'
   76 |         if(qs[i] != ms[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:76:25: note:   '__gnu_cxx::__alloc_traits<std::allocator<card>, card>::value_type' {aka 'card'} is not derived from 'const std::allocator<_CharT>'
   76 |         if(qs[i] != ms[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:76:25: note:   '__gnu_cxx::__alloc_traits<std::allocator<card>, card>::value_type' {aka 'card'} is not derived from 'const std::reverse_iterator<_Iterator>'
   76 |         if(qs[i] != ms[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:76:25: note:   '__gnu_cxx::__alloc_traits<std::allocator<card>, card>::value_type' {aka 'card'} is not derived from 'const std::reverse_iterator<_Iterator>'
   76 |         if(qs[i] != ms[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:76:25: note:   '__gnu_cxx::__alloc_traits<std::allocator<card>, card>::value_type' {aka 'card'} is not derived from 'const std::move_iterator<_IteratorL>'
   76 |         if(qs[i] != ms[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:76:25: note:   '__gnu_cxx::__alloc_traits<std::allocator<card>, card>::value_type' {aka 'card'} is not derived from 'const std::move_iterator<_IteratorL>'
   76 |         if(qs[i] != ms[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:76:25: note:   '__gnu_cxx::__alloc_traits<std::allocator<card>, card>::value_type' {aka 'card'} is not derived from 'const std::pair<_T1, _T2>'
   76 |         if(qs[i] != ms[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:76:25: note:   'card' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   76 |         if(qs[i] != ms[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:76:25: note:   'card' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   76 |         if(qs[i] != ms[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:76:25: note:   'card' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   76 |         if(qs[i] != ms[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:76:25: note:   '__gnu_cxx::__alloc_traits<std::allocator<card>, card>::value_type' {aka 'card'} is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   76 |         if(qs[i] != ms[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:76:25: note:   mismatched types 'const _CharT*' and 'card'
   76 |         if(qs[i] != ms[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:76:25: note:   '__gnu_cxx::__alloc_traits<std::allocator<card>, card>::value_type' {aka 'card'} is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   76 |         if(qs[i] != ms[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:76:25: note:   '__gnu_cxx::__alloc_traits<std::allocator<card>, card>::value_type' {aka 'card'} is not derived from 'const std::tuple<_UTypes ...>'
   76 |         if(qs[i] != ms[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 |