слияние

#include <iostream>
#include <cmath>

using namespace std;

void merge_series (int *arr, int first, int last_1, int last_2, int *dubl)
{
  int i = first;
  int j = last_1+1;
  int c = 0;

 for (c = first; c <= last_2; c++)
  if (j > last_2)
    dubl[c] = arr[i++];
     else if (i > last_1)
      dubl[c] = arr[j++];
      else if (arr[i] <= arr[j])
       dubl[c] = arr[i++];
       else dubl[c] = arr[j++];
}

void sort (int *arr, int first, int last, int *dubl)
{
  int middle = (first + last)/2;

  if (first < middle)
   sort (arr, first, middle, dubl);
  if (middle + 1 < last)
   sort (arr, middle+1, last, dubl);

  merge_series (arr, first, middle, last, dubl);


  for (int i = first; i <= last; i++)
   {
     arr[i] = dubl[i];
     //cout << dubl[i] << " ";
   }
   //cout << endl;
}

void merge_sort (int *arr, int razmer)
{
  int *dubl = new int[razmer];
  sort (arr, 0, razmer-1, dubl);
}

int main()
{
  int n=0;
  cin >> n;

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

  merge_sort (arr, n);

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