ADA-lab-program to merge sorting

#include<iostream>
using namespace std;

void merge(int arr[], int l, int mid, int r){
	int n1=mid-l+1;
	int n2=r-mid;
	
	int a[n1];
	int b[n2]; //temp arrays
	
	for(int i=0;i<n1;i++){
		a[i]=arr[l+i];
	}
	for(int i=0;i<n2;i++){
		b[i]=arr[mid+1+i];
	}
	int i=0;
	int j=0;
	int k=l;
	while(i<n1 && j<n2){
		if(a[i]<b[j]){
			arr[k]=a[i];
			k++; i++;
		}
		else{
			arr[k]=b[j];
			k++; j++;
		}
	}
	while(i<n1){
		arr[k]=a[i];
		k++; i++;
	}
	while(j<n2){
		arr[k]=b[j];
		k++; j++;
	}
}
void mergeSort(int arr[], int l, int r){
	if(l<r){
		int mid=(l+r)/2;
		mergeSort(arr,l,mid);
		mergeSort(arr,mid+1,r);
		
		merge(arr,l,mid,r);
	}
}
int main(){
	int arr[]={5,4,33,2,31};
	mergeSort(arr,0,4);
	for(int i=0;i<5;i++){
		cout<<arr[i]<<" ";
	}
	cout<<endl;
	return 0;
}