Merge sort DSA

#include <iostream>
using namespace std;

class merg{
    int arr[10] = {1, 44, 32, 12, 43, 89, 41, 78, 11, 10};
public:
    void merge(int l, int m, int r) {
       int i, j, k, nl, nr;
       nl = m-l+1; nr = r-m;
       int leftarr[nl], rightarr[nr];

       for(i = 0; i<nl; i++)
          leftarr[i] = arr[l+i];
       for(j = 0; j<nr; j++)
          rightarr[j] = arr[m+1+j];

       i = 0; j = 0; k = l;
       while(i < nl && j<nr) {
          if(leftarr[i] <= rightarr[j]) {
             arr[k] = leftarr[i];
             i++;
          }else{
             arr[k] = rightarr[j];
             j++;
          }
          k++;
       }

       while(i<nl) {
          arr[k] = leftarr[i];
          i++; k++;
       }
       while(j<nr) {
          arr[k] = rightarr[j];
          j++; k++;
       }
    }

    void mergesort(int start, int end){
        if(start < end){
            int middle = (start + end)/2;
            mergesort(start, middle);
            mergesort(middle + 1, end);
            merge(start, middle, end);
        }
        else{
            return;
        }
    }

    void display(){
        cout << "Sorted:";
        for(int i = 0; i < 10; i++){
            cout << " " << arr[i];
        }
    }
};

int main(){
    merg n;
    n.mergesort(0, 9);
    n.display();
    return 0;
}