What's the quickest way to find if a number is power of 2?

v_d_d · 2003-03-18T20:25:52

What''s the quickest way to find if a given number is a power of 2?

Math and Physics Programming

Started by v_d_d March 13, 2003 11:42 AM

13 comments, last by v_d_d 21 years, 11 months ago

Null and Void

1,088

March 13, 2003 12:44 PM

  bool IntegerIsPowerOfTwo(int Val) {	return ((Val-1) & Val) == 0;}

Enselic

829

March 13, 2003 12:53 PM

Hehe, that''d be the fastest. But it should be:

bool IntegerIsPowerOfTwo(int Val){    if( Val == 0 )        return false;    return ((Val-1) & Val) == 0;}

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v_d_d

Author

122

March 13, 2003 01:07 PM

Thanks guys!

Here is a link I found on the subject:

http://www.bebox.dircon.co.uk/power2.htm

:-)

tferguson

122

March 18, 2003 07:59 PM

Oops....made a stupid reading mistake I thought it was referring to even/odd.....

[edited by - tferguson on March 18, 2003 9:01:27 PM]

Beer Hunter

712

March 18, 2003 08:25 PM

Just for fun...

  // IEEE floats onlybool isPowerOf2(float f){  unsigned int foo = reinterpret_cast<int&>(f);  return ((foo & 0x7F800000u) != 0) && ((foo & 0x807FFFFF) == 0);}

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What's the quickest way to find if a number is power of 2?

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