How do I extract digit in an integer using bitwise operator

Question

How do I extract digits from an integer using bitwise operator. i.e. I want to extract 234 in the integer n=123456 I know this is possible using and, or, xor bitwise operator but I'm not sure How? thnx

Answer 1

If you don't want bitwise at this point, I believe you can extract individual digits like this:

int digitAtPos(int number, int pos)
{
   return ( number / (int)pow(10.0, pos-1) ) % 10;
}

I'm not sure if this is the fastest/most-efficient way, but it works.

Stitching the digits back together should be easy as well, just multiply by increasing powers of ten.

If anyone has a better solution, please tell.

Answer 2

Since this is tagged as homework, i'm only going to explain basic concepts, I'm not actually going to produce an answer.

You use bitwise operations to extract individual bits of a base 2 number. So if your number is 10110101, and you want to get the 0101 at the end, you would have to set up a mask, and then do a binary anding to filter out the unimportant digits. Your mask should look something like 00001111. When you and them together, only the digits you want are remaining.

10110101 & 00001111 == 00000101