// further simplifying:
int fncSpecialBinary(int n){
return ~n&-n&n>>1;
}

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kevinvw1Author Commented:

Rgonzo1971... nope, not my homework. If your username is any indication of your age, I am older than you and have not been in school since the 80s. :)
But since you went there...
Your answer works good for an Introduction to Programming 101 Junior college course.
But Ozo's answer is definitely Grad School material.

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Marcos Freitas de MoraisCommented:

I thought about signed signed numbers, precisely ones' complement and I wanna post some comments about accepted solution.

If we use this algorithm by ones' complement for number 4, we have something like:

(~4 & 11 & 4>>1) // 11 is negative value to 4 and this sentece return true

mccarlIT Business Systems Analyst / Software DeveloperCommented:

@DiSalomao,

I think you are confusing your 'ones' and 'twos' complements. -n gives you the *twos* complement of n, ie. if n is 4 (and if we are talking 4-bit numbers as in your example) then -n is 12 (not 11)... and the result evaluates to false which is correct!

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Marcos Freitas de MoraisCommented:

Mccarl,

There is no mistakes. I have a x86 machine and for me the accepted solution works fine, too. Why ? My computer donĀ“t use ones' complement to represent negative numbers.

But, if you get the code {... return ~n&-n&n>>1;...} and compile on computers that use ones' complement to represent their negative numbers, you'll get a bug. By the way, on that kind of machines -4 (decimal) == 1011 (binay) == 11 (unsigned decimal).

I just propose my code, because it's more portable one and to justify my comments.

The C language standard does allow for ones complement or sign/magnitude representation, although I'm not familiar with any computer architecture that's used them since the 1960's
If you are running on such a computer, you can use
unsigned int fncSpecialBinary(unsigned int n){
return ~n&(~n+1)&n>>1;
}

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Basically, you should do your homework alone

Here is my pseudo-code

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