How to shift array elements

Question

Hi,

I have an array of n = 32 items with positive and negative values. First n/2 elements are positive and sorted by value and second n/2 elements are negative and sorted by value as well. I would like to sort the whole array by value, starting from the smallest negative value to biggest positive value which means if there are 32 elements the first 16 (n/2) sorted elements should contain the values of second 16 elements of the original array and the second 16 elements of the sorted array should contain the first 16 values of the original array.

Hypothetical example:

double[] original = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, -16, -15, ..., -1};

double[] sorted = {-16, -15, ...., -1, 1, 2, ..., 16};

Does anyone know what is the best way to shift the elements to generate the sorted array from original?

This array is by the way tied to another array which doesn't have the elements sorted by size the same way and has to be shifted the same way as original so the array shouldn't be sorted by size, it has to be shifted.

Answer 1

Just do a swap on element 0 and element 16, 1 and 17, 2 and 18.. etc.

Answer 2

Have you tried:

Array.Sort(original);

Answer 3

So you want a second array, with the contents of the original but at locations shifted? Either do it explicitly:

double[] result = new double[32];
for (int i=0; i < 32; i++)
{
    result[(i+16)%32] = original[i];
}

or using Array.Copy twice:

double[] result = new double[32];
Array.Copy(original, 0, result, 16, 16);
Array.Copy(original, 16, result, 0, 16);

Answer 4

How about in Linq:

int half = original.Length/2;
var sorted = original.Skip(half).Concat(original.Take(half)).ToArray();

Answer 5

Do you want to sort one array based on the values contained in another array of the same size? If so, use the following:

Array.Sort(keys, values);

Here's the documentation Array.Sort(Array keys, Array items)

Answer 6

Given the rigid nature of the problem, Array.Copy:

        int half = original.Length / 2;
        Array.Copy(original, 0, sorted, half, half);
        Array.Copy(original, half, sorted, 0, half);