Language: C

void mergeSort(int*, int, int);


int main(){

  int i;
  int A[MAX], n;
  
   count = 0;
   
  scanf("%d", &n);
  for ( i = 0; i < n; i++ ) {
    scanf("%d", &A[i]);
    if (A[i] >= INFTY ){
      return 1;
    }
  }
  
  mergeSort(A, 0, n);

  for ( i = 0; i < n; i++ ) {
    if ( i ) printf(" ");
    printf("%d", A[i]);
    }
  printf("\n");

  printf("%d\n", count);

  return 0;
}


void merge(int A[], int left, int mid, int right){
  
  int i, j, k;

  int n1, n2;

   n1 = mid - left;
   n2 = right - mid;
   
   for ( i = 0; i < n1; i++ ){
     L[i] = A[left + i];
   }
   
   for ( i = 0; i < n2; i++ ){
     R[i] = A[mid + i];
   }
   
  L[n1] = INFTY;
  R[n2] = INFTY;
  
  i = 0;
  j = 0;
  
  for ( k = left; k < right; k++ ){
    
    count++;
    
    if ( L[i] <= R[j] ){
      A[k] = L[i];
      i = i + 1;
    }
    else {
      A[k] = R[j];
      j = j + 1;
    }
  }
}


void mergeSort(int A[], int left, int right ){
  
  int mid;
  
  if ( left + 1 < right ){
    
    mid = (left + right)/2;
    mergeSort(A, left, mid);
    mergeSort(A, mid, right);
    merge(A, left, mid, right);
    
  }
}

Compiler output:
main.c: In function 'main':
main.c:7:9: error: 'MAX' undeclared (first use in this function)
    7 |   int A[MAX], n;
      |         ^~~
main.c:7:9: note: each undeclared identifier is reported only once for each function it appears in
main.c:9:4: error: 'count' undeclared (first use in this function)
    9 |    count = 0;
      |    ^~~~~
main.c:11:3: error: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
   11 |   scanf("%d", &n);
      |   ^~~~~
main.c:1:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
  +++ |+#include <stdio.h>
    1 | void mergeSort(int*, int, int);
main.c:11:3: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
   11 |   scanf("%d", &n);
      |   ^~~~~
main.c:11:3: note: include '<stdio.h>' or provide a declaration of 'scanf'
main.c:14:17: error: 'INFTY' undeclared (first use in this function)
   14 |     if (A[i] >= INFTY ){
      |                 ^~~~~
main.c:22:14: error: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
   22 |     if ( i ) printf(" ");
      |              ^~~~~~
main.c:22:14: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:22:14: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
main.c:22:14: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:23:5: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
   23 |     printf("%d", A[i]);
      |     ^~~~~~
main.c:23:5: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:25:3: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
   25 |   printf("\n");
      |   ^~~~~~
main.c:25:3: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c: In function 'merge':
main.c:43:6: error: 'L' undeclared (first use in this function)
   43 |      L[i] = A[left + i];
      |      ^
main.c:47:6: error: 'R' undeclared (first use in this function)
   47 |      R[i] = A[mid + i];
      |      ^
main.c:50:11: error: 'INFTY' undeclared (first use in this function)
   50 |   L[n1] = INFTY;
      |           ^~~~~
main.c:58:5: error: 'count' undeclared (first use in this function)
   58 |     count++;
      |     ^~~~~