Language: C

#include <stdio.h>
#define  MAX 500000
int S[MAX],count=0;
void merge(int, int, int, int);
void mergeSort(int, int, int);
int main()
{
  int n,i;
  scanf("%d",&n);
  for(i = 0;i < n;i++)
    scanf("%d",&S[i]);
  mergeSort(S,0,n);
  for(i = 0;i < n;i++){
    printf("%d",S[i]);
    if(i < n-1) printf(" ");
  }
  printf("\n");
  printf("%d\n",count);
  return 0;
}

void merge(int A[], int left,int mid, int right)
{
  int n1,n2,i,j,k;
  int *L,*R;
  n1 = mid - left;
  n2 = right - mid;
  L = (int *)malloc(sizeof(int)*(n1+1));
  R = (int *)malloc(sizeof(int)*(n2+1));
  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++){
    if(L[i] <= R[j]){
      A[k] = L[i];
      i++;
      count++;
    }
    else{
      A[k] = R[j];
      j++;
      count++;
    }
  }
  free(L);
  free(R);
}

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:12:13: error: passing argument 1 of 'mergeSort' makes integer from pointer without a cast [-Wint-conversion]
   12 |   mergeSort(S,0,n);
      |             ^
      |             |
      |             int *
main.c:5:16: note: expected 'int' but argument is of type 'int *'
    5 | void mergeSort(int, int, int);
      |                ^~~
main.c: At top level:
main.c:22:6: error: conflicting types for 'merge'; have 'void(int *, int,  int,  int)'
   22 | void merge(int A[], int left,int mid, int right)
      |      ^~~~~
main.c:4:6: note: previous declaration of 'merge' with type 'void(int,  int,  int,  int)'
    4 | void merge(int, int, int, int);
      |      ^~~~~
main.c: In function 'merge':
main.c:28:14: error: implicit declaration of function 'malloc' [-Wimplicit-function-declaration]
   28 |   L = (int *)malloc(sizeof(int)*(n1+1));
      |              ^~~~~~
main.c:2:1: note: include '<stdlib.h>' or provide a declaration of 'malloc'
    1 | #include <stdio.h>
  +++ |+#include <stdlib.h>
    2 | #define  MAX 500000
main.c:28:14: warning: incompatible implicit declaration of built-in function 'malloc' [-Wbuiltin-declaration-mismatch]
   28 |   L = (int *)malloc(sizeof(int)*(n1+1));
      |              ^~~~~~
main.c:28:14: note: include '<stdlib.h>' or provide a declaration of 'malloc'
main.c:36:11: error: 'INFTY' undeclared (first use in this function)
   36 |   L[n1] = INFTY;
      |           ^~~~~
main.c:36:11: note: each undeclared identifier is reported only once for each function it appears in
main.c:52:3: error: implicit declaration of function 'free' [-Wimplicit-function-declaration]
   52 |   free(L);
      |   ^~~~
main.c:52:3: note: include '<stdlib.h>' or provide a declaration of 'free'
main.c:52:3: warning: incompatible implicit declaration of built-in function 'free' [-Wbuiltin-declaration-mismatch]
main.c:52:3: note: include '<stdlib.h>' or provide a declaration of 'free'
main.c: At top level:
main.c:56:6: error: conflicting types for 'mergeSort'; have 'void(int *, int,  int)'
   56 | void mergeSort(int A[], int left, int right)
      |      ^~~~~~~~~
main.c:5:6: note: previous declaration of 'mergeSort' with type 'void(int,  int,  int)'
    5 | void mergeSort(int, int, int);
      |      ^~~~~~~~~