Templates for merge sorting objects that implemented operator<=

mergeSort.h

#pragma once
#include<memory>

namespace MergeSort_internal
{
    template <typename T>
    void merge(T* arr, int l, int m, int r)
    {
        int i, j, k;
        int n1 = m - l + 1;
        int n2 = r - m;

        std::unique_ptr<T[]> L = std::make_unique<T[]>(n1);
        std::unique_ptr<T[]> R = std::make_unique<T[]>(n2);

        for (i = 0; i < n1; i++)
            L[i] = arr[l + i];
        for (j = 0; j < n2; j++)
            R[j] = arr[m + 1 + j];

        i = 0;
        j = 0;
        k = l;
        while (i < n1 && j < n2) {
            if (L[i] <= R[j]) {
                arr[k] = L[i];
                i++;
            }
            else {
                arr[k] = R[j];
                j++;
            }
            k++;
        }

        while (i < n1) {
            arr[k] = L[i];
            i++;
            k++;
        }

        while (j < n2) {
            arr[k] = R[j];
            j++;
            k++;
        }
    }

    template <typename T>
    void sort(T* arr, int l, int r)
    {
        if (l < r) {
            int m = (l + r) / 2;
            sort(arr, l, m);
            sort(arr, m + 1, r);
            merge(arr, l, m, r);
        }
    }
}

template <typename T>
void mergeSort(T* arr, int l)
{
    MergeSort_internal::sort(arr, 0, l);
}

test.cpp

#include<mergeSort.h>
#include<iostream>
#include<vector>

int main()
{
  std::vector<int> values = { 5 , 3, 82, 1, 53, 2, 1000 };
  mergeSort(values.data(), values.size());
  for(size_t v = 0; v < values.size(); v ++)
  {
   std::cout << values[v] << std::endl; 
  }
  return 0; 
}