Merge sort

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
void merge(int arr[],int left, int mid, int right)
{
    int l_size = (mid-left)+1;
    int r_size = right-mid;

    int l_arr[l_size],r_arr[r_size];
    for(int i=0;i<l_size;i++)
        l_arr[i] = arr[left+i];
    for(int i=0;i<r_size;i++)
        r_arr[i] = arr[mid+1+i];

    int i=0,j=0,k=left;
    while(i<l_size and j<r_size)
    {
        if(l_arr[i]<=r_arr[j])
        {
            arr[k] = l_arr[i];
            i++;
        }
        else
        {
            arr[k] = r_arr[j];
            j++;
        }
        k++;
    }
    while(i<l_size)
    {
        arr[k] = l_arr[i];
        i++;
        k++;
    }
    while(j<r_size)
    {
        arr[k] = r_arr[j];
        j++;
        k++;
    }
}

void mergesort(int arr[],int left,int right)
{
    if(left>=right)
        return;
    int mid = left+(right-left)/2;
    mergesort(arr,left,mid);
    mergesort(arr,mid+1,right);
    merge(arr,left,mid,right);
}

int main()
{
    #ifndef ONLINE_JUDGE
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif

    int n;
    cin >> n;
    int arr[n];
    for(int i=0;i<n;i++)
        cin >> arr[i];

    mergesort(arr,0,n-1);

    for(int i=0;i<n;i++)
        cout << arr[i] << ' ';

    return 0;
}