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**AV****Guest**

You are given a number n and you have to find if its divisble by 3 but the catch is you cant use mod or division operations

i am looking for something using binary arithmetic

**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,686

I recall using integer division in the past. It had special methods that may suit you.

Now if I could only find what I did with it ....

... I did find this: http://www.bearcave.com/software/divide.htm , the author has some C code that might do it for you.

The central part of his code has:

while (remainder < divisor) {

bit = (dividend & 0x80000000) >> 31;

remainder = (remainder << 1) | bit;

d = dividend;

dividend = dividend << 1;

num_bits--;

}

(he says that always goes one step too far, so he just backs up once.)

Is that what you were looking for?

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