Language: C

#include<stdio.h>
??
typedef struct {
????????char mark;
????????int num;
}card;
??
void swap(card *a,card *b);
int partition(card A[], int p, int r);
void quickSort(card A[], int p, int r);
??
int partition(card A[], int p, int r){
????????int x=A[r].num;
????????int i=p-1,j;
????????for(j=p;j<r;j++){
????????????????if(A[j].num<=x){
????????????????????????i++;
????????????????????????swap(&(A[i]),&(A[j]));
????????????????}
????????}
????????swap(&(A[i+1]),&(A[r]));
????????return i+1;
}
??
void swap(card *a,card *b){
????????card tmp;
????????tmp=*a;
????????*a=*b;
????????*b=tmp;
}
??
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(void){
????????static card A[100000],copy[100000];
????????int n,base;
????????int i,j;
????????char mark_checker[4],checker_crt,check_num;
????????int s_flag=1;
????????scanf("%d%*c",&n);
????????for(i=0;i<n;i++){
????????????????scanf("%c%d%*c",&(A[i].mark),&(A[i].num));
????????}
????????for(i=0;i<n;i++){
????????????????copy[i]=A[i];
????????}
????????quickSort(A,0,n-1);
????????for(i=0;i<n-1;i++){
????????????????if(A[i].num==A[i+1].num){
????????????????????????base=A[i].num;
????????????????????????mark_checker[0]=A[i].mark;
????????????????????????mark_checker[1]=A[i+1].mark;
????????????????????????if(i+2<n && base==A[i+2].num){
????????????????????????????????mark_checker[2]=A[i+2].mark;
????????????????????????????????if(i+3<n && base==A[i+3].num){
????????????????????????????????????????mark_checker[3]=A[i+3].mark;
????????????????????????????????????????i=i+3;
????????????????????????????????????????check_num=3;
????????????????????????????????}else{
????????????????????????????????????????i=i+2;
????????????????????????????????????????check_num=3;
????????????????????????????????}
????????????????????????}else{
????????????????????????????????i=i+1;
????????????????????????????????check_num=2;
????????????????????????}
????????????????????????checker_crt=0;
????????????????????????for(j=0;j<n;j++){
????????????????????????????????if(copy[j].num==base){
????????????????????????????????????????if(mark_checker[checker_crt++]!=copy[j].mark){
????????????????????????????????????????????????s_flag=0;
????????????????????????????????????????}
????????????????????????????????????????if(checker_crt>check_num-1){
????????????????????????????????????????????????break;
????????????????????????????????????????}
????????????????????????????????}
????????????????????????}
????????????????}
????????}???????????? 
????????if(s_flag){
????????????????printf("Stable\n");
????????}else{
????????????????printf("Not stable\n");
????????}???? 
????????for(i=0;i<n;i++){
????????????????printf("%c %d\n",A[i].mark,A[i].num);
????????}
????????return 0;
}

Compiler output:
main.c:2:1: error: expected identifier or '(' before '?' token
    2 | ??
      | ^
main.c:6:2: warning: data definition has no type or storage class
    6 | }card;
      |  ^~~~
main.c:6:2: error: type defaults to 'int' in declaration of 'card' [-Wimplicit-int]
main.c:7:1: error: expected identifier or '(' before '?' token
    7 | ??
      | ^
main.c:9:15: error: expected declaration specifiers or '...' before 'card'
    9 | int partition(card A[], int p, int r);
      |               ^~~~
main.c:10:16: error: expected declaration specifiers or '...' before 'card'
   10 | void quickSort(card A[], int p, int r);
      |                ^~~~
main.c:11:1: error: expected identifier or '(' before '?' token
   11 | ??
      | ^
main.c:24:1: error: expected identifier or '(' before '?' token
   24 | ??
      | ^
main.c:31:1: error: expected identifier or '(' before '?' token
   31 | ??
      | ^
main.c:39:1: error: expected identifier or '(' before '?' token
   39 | ??
      | ^