mergeSort.cpp

#include <iostream>
using namespace std;

void merge(int arr[], int l, int m, int r)
{
    int i, j, k;
    int n1 = m - l + 1;
    int n2 =  r - m;
 
    int L[n1], R[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++;
    }
}
void mergeSort(int arr[], int l, int r)
{
   if (l < r)
   {
      int m = l+(r-l)/2;
      mergeSort(arr, l, m);
      mergeSort(arr, m+1, r);
      merge(arr, l, m, r);
   }
}
 

 
void print(int A[], int size)
{
    int i;
    for (i=0; i < size; i++)
        cout<<A[i]<<((i==size-1)?"":" ,");
}
 
int main()
{
    int arr[] = {1,5,7,8,9,4,5,6,7,8};
    int arr_size = 10;
  
    mergeSort(arr, 0, arr_size - 1);
 
    print(arr, arr_size);
    return 0;
}