Comments on: I’ve Got the Power (of 2) http://www.technicalinterviews.net/ive-got-the-power-of-2/ This site features a collection of common technical interview questions gathered by a group of programmers who have been through, and given, lots of technical interviews. There is an emphasis on C++ and game programming technical interviews, but most of the questions are relevant to any technical interview. Thu, 04 Dec 2008 19:20:52 +0000 http://wordpress.org/?v=2.0.7 by: Toddsa http://www.technicalinterviews.net/ive-got-the-power-of-2/#comment-150 Sun, 04 Mar 2007 23:14:03 +0000 http://www.technicalinterviews.net/ive-got-the-power-of-2/#comment-150 given x as an integer (x & (x-1)) will be 0 if x is a power of 2 and non zero if it is not. The reason is all power of 2's in binary will have a single set bit and (x-1) will have all set bits excluding x. for example x = 8 in binary is 1000 and (x-1) or 7 in binary is 111 so if you use the & operator you will get. 1000 & 0111 ------ 0000 Any x this is not a power of 2 will result in some other non 0 result. given x as an integer

(x & (x-1)) will be 0 if x is a power of 2 and non zero if it is not. The reason is all power of 2’s in binary will have a single set bit and (x-1) will have all set bits excluding x. for example x = 8 in binary is 1000 and (x-1) or 7 in binary is 111 so if you use the & operator you will get.

1000
& 0111
——
0000

Any x this is not a power of 2 will result in some other non 0 result.

]]> by: Robin http://www.technicalinterviews.net/ive-got-the-power-of-2/#comment-45 Thu, 01 Feb 2007 21:40:45 +0000 http://www.technicalinterviews.net/ive-got-the-power-of-2/#comment-45 This will be 0 if only one bit. otherwise, it is non-zero. This will be 0 if only one bit.
otherwise, it is non-zero.

]]> by: Robin http://www.technicalinterviews.net/ive-got-the-power-of-2/#comment-44 Thu, 01 Feb 2007 21:39:43 +0000 http://www.technicalinterviews.net/ive-got-the-power-of-2/#comment-44 I could not put in the leftshit operator. Answer is: X leftshift by 1 bit & X leftshift by 2 bits & X leftshift by 3 bits I could not put in the leftshit operator.

Answer is:

X leftshift by 1 bit &
X leftshift by 2 bits &
X leftshift by 3 bits

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