Merge problem, C++ (gcc)

Merge problem

/**
  * Divide  : Divide the n-element array into two n/2-element
  *           sub-arrays
  * Conquer : Sort the two sub-arrays recursively using
  *           merge sort
  * Combine : Merge the two sorted subsequences to form the
  *           sorted array
  **/

#include<stdio.h>

int arr[20];       // array to be sorted

int main()
{

int n,i;
  clrscr();
  printf("Enter the size of array\n");  // input the elements
  scanf("%d",&n);
  printf("Enter the elements:");
  for(i=0; i<n; i++)
    scanf("%d",&arr[i]);

merge_sort(arr,0,n-1);  // sort the array

printf("Sorted array:");  // print sorted array
  for(i=0; i<n; i++)
    printf("%d",arr[i]);
   getch();
  return 0;
}

int merge_sort(int arr[],int low,int high)
{
  int mid; int i;
  if(low<high) {

mid=(low+high)/2;
    // Divide and Conquer
    merge_sort(arr,low,mid);
    merge_sort(arr,mid+1,high);
    // Combine

merge(arr,low,mid,high);
  }

return 0;
}

int merge(int arr[],int l,int m,int h)
{
  int arr1[10],arr2[10];  // Two temporary arrays to
  //hold the two arrays to be merged
  int n1,n2,i,j,k,z;

i=0;j=0;

for(z=l;z<=m;z++)
	{
		arr1[i]=arr[z];
		i++;
	}
	for(z=m+1;z<=h;z++)
	{
		arr2[j]=arr[z];
		j++;
	}

n1=i;
  n2=j;
  i=0;
  j=0;
  for(k=l; k<=h; k++)
  { //process of combining two sorted arrays

if(i<n1 && j<n2)
    {
	 if(arr1[i]<=arr2[j])
	      arr[k]=arr1[i++];
	else
	     arr[k]=arr2[j++];
     }
     else if(i>=n1)
     {
	  arr[k]=arr[j++];
     }
     else
     {
	 arr[k]=arr[i++];
     }

}

return 0;
}


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