I need to shift to the right and to the left an array by N places.
The items that pop out on the side where i shift to must get back into on the other side.
Shift right by 13:
[0,1,2,3,4,5,6,7,8,9] -> [7,8,9,0,1,2,3,4,5,6]
Shift left by 15:
[0,1,2,3,4,5,6,7,8,9] -> [5,6,7,8,9,0,1,2,3,4]
This operation will happen millions of times and must be really fast.
My current implementation is the following. Please have a look and suggest if there is some optimization to do.
if (shift > 0)
{
int offset = array.Length % shift;
if (offset > 0)
{
byte[] temp = new byte[offset];
if (!right)
{
Array.Copy(array, temp, offset);
Array.Copy(array, offset, array, 0, array.Length - offset);
Array.Copy(temp, 0, array, array.Length - offset, temp.Length);
}
else
{
Array.Copy(array, array.Length - offset, temp, 0, offset);
Array.Copy(array, 0, array, offset, array.Length - offset);
Array.Copy(temp, 0, array, 0, temp.Length);
}
}
}
As a tip on how much it will get shifted (but I doubt it can lead to optimization):
- depends on the entropy of the array itself
- for aray that are full of same values it will get shifted roughtly 0
- more entropy means higher shift value
- direction of shift will be used generally more to the left
PS. Cannot get the security permission to run unsafe code :/
PS2: The resulting array must be passed as an array onward to a different library for further processing, so I cannot just wrap and reindex.
PS3: I'd prefer to work on the same array since the method uses ref, and doing that on a new array and then copying back would be time consuming (i'm using the 'temp' array for the part that falls out because of shifting).