temp.merge.reduc

#include<bits/stdc++.h>
using namespace std;
void merge(int arr[], int l, int m, int r)
{  int j,i, k;
    int n1 = m - l + 1;
    int n2 = r - m;
    int L[n1], R[n2];
/* Copy data to temp arrays L[] and R[] */
    for (i = 0; i < n1; i++)
        L[i] = arr[l + i];
    for (j = 0; j < n2; j++)
        R[j] = arr[m + 1+ j];
/* Merge the temp arrays back into arr[l..r]*/
    i = 0; // Initial index of first subarray
    j = 0; // Initial index of second subarray
    k = l; // Initial index of merged subarray
 while (i < n1 && j < n2)
    { if (L[i] <= R[j])
        {       arr[k] = L[i];
            i++;  }
        else
        {      arr[k] = R[j];
            j++;  }
        k++;}
/* Copy the remaining elements of L[], if there  are any */
    while (i < n1)
    {arr[k] = L[i];
        i++;
        k++;}
    /* Copy the remaining elements of R[], if there  are any */
    while (j < n2)
    {   arr[k] = R[j];
        j++;
        k++;  }}
/* l is for left index and r is right index of the
sub-array of arr to be sorted */
void mergeSort(int arr[], int l, int r)
{   if (l < r)
    {
        // Same as (l+r)/2, but avoids overflow for
        // large l and h
        int m = (l+r)/2;
     // Sort first and second halves
        mergeSort(arr, l, m);
        mergeSort(arr, m+1, r);

        merge(arr, l, m, r);
    }
}

/* Function to print an array */
void printArray(int A[], int size)
{
    int i;
    for (i=0; i < size; i++)
        cout<< A[i]<<"  ";

printf("\n");
}
/* Driver program to test above functions */
int main()
{    int arr[] = {12, 11, 13, 5, 6, 7};
    int arr_size = sizeof(arr)/sizeof(arr[0]);

    printf("Given array is \n");
    printArray(arr, arr_size);
    mergeSort(arr, 0, arr_size - 1);
printf("\nSorted array is \n");
    printArray(arr, arr_size);
    return 0;
}