Language: C

void quicksort(int p, int r);
int partition(int p,int r);
int isStable(char in[N],char out[N],int in1[N],int out1[N],int n);
int main(){
  int i,n;
scanf("%d",&n);
 for(i=0;i<n;i++){
   scanf(" %c %d",&A[i],&A1[i]);
   B[i]=A[i];
   B1[i]=A1[i];
 }
 quicksort(0,n-1);
 
 
 if(isStable(&A[0],&B[0],&A1[0],&B1[0],n)==0) printf("Not stable\n");
 else printf("Stable\n");
 for(i=0;i<n;i++){
   printf("%c %d\n",A[i],A1[i]);
   }
 return 0;
}

void quicksort(int p, int r){
  int q;
  if (p < r){
    q = partition(p, r);
    quicksort(p, q-1);
    quicksort(q+1, r);
  }
}
int partition(int p,int r){
  int i,j,x,change1;
  char change; 
  x =A1[r];
  i = p-1;
  for(j = p;j<r;j++){
    if(A1[j]<=x){
      i = i+1;
      change=A[i];
      A[i]= A[j];
      A[j]=change;

      change1=A1[i];
      A1[i]= A1[j];
      A1[j]=change1;
    }
  }
  change=A[i+1];
  A[i+1]=A[r];
  A[r]=change;
  
  change1=A1[i+1];
  A1[i+1]=A1[r];
  A1[r]=change1;
  
  return i+1;
}

int isStable(char in[N],char out[N],int in1[N],int out1[N],int n){
  
  int i,j,a,b;
  
  for(i=0;i<n;i++){
    for(j=i+1;j<n;j++){
      for(a=0;a<n;a++){
	for(b=a+1;b<n;b++){
	  if(in1[i]==in1[j] && in[i]==out[b] && in[j] == out[a] && in1[i]==out1[b] && in1[j] == out1[a]){
	    return 0;
	  }
	}
      }
    }
  }
  return 1;
}

Compiler output:
main.c:3:22: error: 'N' undeclared here (not in a function)
    3 | int isStable(char in[N],char out[N],int in1[N],int out1[N],int n);
      |                      ^
main.c: In function 'main':
main.c:6:1: error: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    6 | scanf("%d",&n);
      | ^~~~~
main.c:1:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
  +++ |+#include <stdio.h>
    1 | void quicksort(int p, int r);
main.c:6:1: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
    6 | scanf("%d",&n);
      | ^~~~~
main.c:6:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
main.c:8:20: error: 'A' undeclared (first use in this function)
    8 |    scanf(" %c %d",&A[i],&A1[i]);
      |                    ^
main.c:8:20: note: each undeclared identifier is reported only once for each function it appears in
main.c:8:26: error: 'A1' undeclared (first use in this function)
    8 |    scanf(" %c %d",&A[i],&A1[i]);
      |                          ^~
main.c:9:4: error: 'B' undeclared (first use in this function)
    9 |    B[i]=A[i];
      |    ^
main.c:10:4: error: 'B1' undeclared (first use in this function)
   10 |    B1[i]=A1[i];
      |    ^~
main.c:15:14: error: type of formal parameter 1 is incomplete
   15 |  if(isStable(&A[0],&B[0],&A1[0],&B1[0],n)==0) printf("Not stable\n");
      |              ^~~~~
main.c:15:20: error: type of formal parameter 2 is incomplete
   15 |  if(isStable(&A[0],&B[0],&A1[0],&B1[0],n)==0) printf("Not stable\n");
      |                    ^~~~~
main.c:15:26: error: type of formal parameter 3 is incomplete
   15 |  if(isStable(&A[0],&B[0],&A1[0],&B1[0],n)==0) printf("Not stable\n");
      |                          ^~~~~~
main.c:15:33: error: type of formal parameter 4 is incomplete
   15 |  if(isStable(&A[0],&B[0],&A1[0],&B1[0],n)==0) printf("Not stable\n");
      |                                 ^~~~~~
main.c:15:47: error: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
   15 |  if(isStable(&A[0],&B[0],&A1[0],&B1[0],n)==0) printf("Not stable\n");
      |                                               ^~~~~~
main.c:15:47: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:15:47: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
main.c:15:47: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:16:7: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
   16 |  else printf("Stable\n");
      |       ^~~~~~
main.c:16:7: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:18:4: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
   18 |    printf("%c %d\n",A[i],A1[i]);
      |    ^~~~~~
main.c:18:4: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c: In function 'partition':
main.c:34:6: error: 'A1' undeclared (first use in this function)
   34 |   x =A1[r];
      |      ^~
main.c:39:14: error: 'A' undeclared (first use in this function)
   39 |       change=A[i];
      |              ^
main.c: At top level:
main.c:59:22: error: 'N' undeclared here (not in a function)
   59 | int isStable(char in[N],char out[N],int in1[N],int out1[N],int n){
      |                      ^