[R] Please help translate this program in C++ to R

[Boris Steipe]

See this thread why that's a bad idea ...
 https://stackoverflow.com/questions/26080716/merge-sort-in-r

... and use the code given there, or give us some context why a literal translation would be important to you.

Cheers,
Boris




> On 2019-12-15, at 05:37, Александр Дубровский <dubrovvsskkyy using gmail.com> wrote:
> 
> /* Iterative C program for merge sort */
> #include<stdlib.h>
> #include<stdio.h>
> 
> /* Function to merge the two haves arr[l..m] and arr[m+1..r] of array arr[]
> */
> void merge(int arr[], int l, int m, int r);
> 
> // Utility function to find minimum of two integers
> int min(int x, int y) { return (x<y)? x :y; }
> 
> 
> /* Iterative mergesort function to sort arr[0...n-1] */
> void mergeSort(int arr[], int n)
> {
>   int curr_size;  // For current size of subarrays to be merged
>                   // curr_size varies from 1 to n/2
>   int left_start; // For picking starting index of left subarray
>                   // to be merged
> 
>   // Merge subarrays in bottom up manner.  First merge subarrays of
>   // size 1 to create sorted subarrays of size 2, then merge subarrays
>   // of size 2 to create sorted subarrays of size 4, and so on.
>   for (curr_size=1; curr_size<=n-1; curr_size = 2*curr_size)
>   {
>       // Pick starting point of different subarrays of current size
>       for (left_start=0; left_start<n-1; left_start += 2*curr_size)
>       {
>           // Find ending point of left subarray. mid+1 is starting
>           // point of right
>           int mid = min(left_start + curr_size - 1, n-1);
> 
>           int right_end = min(left_start + 2*curr_size - 1, n-1);
> 
>           // Merge Subarrays arr[left_start...mid] &
> arr[mid+1...right_end]
>           merge(arr, left_start, mid, right_end);
>       }
>   }
> }
> 
> /* Function to merge the two haves arr[l..m] and arr[m+1..r] of array arr[]
> */
> void merge(int arr[], int l, int m, int r)
> {
>    int i, j, k;
>    int n1 = m - l + 1;
>    int n2 =  r - m;
> 
>    /* create temp arrays */
>    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;
>    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++;
>    }
> 
>    /* 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++;
>    }
> }
> 
> /* Function to print an array */
> void printArray(int A[], int size)
> {
>    int i;
>    for (i=0; i < size; i++)
>        printf("%d ", A[i]);
>    printf("\n");
> }
> 
> /* Driver program to test above functions */
> int main()
> {
>    int arr[] = {12, 11, 13, 5, 6, 7};
>    int n = sizeof(arr)/sizeof(arr[0]);
> 
>    printf("Given array is \n");
>    printArray(arr, n);
> 
>    mergeSort(arr, n);
> 
>    printf("\nSorted array is \n");
>    printArray(arr, n);
>    return 0;
> }
> 
> 	[[alternative HTML version deleted]]
> 
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