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Home » Archive » 2006 » May » 31 » A couple of solutions...
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Daily link icon Wednesday, May 31, 2006

A couple of solutions...

def isPowerOf2(num):
  return num == 1 or num == 2 or (num%2 == 0 and isPowerOf2(num/2))
def isPowerOf2(num):
  count = 0
  while(num > 0):
    count += num%2
    num >>= 1
  return count == 1

Update: From David, in the comments:

def isPowerOf2(num):
  return (num & (num - 1) == 0)

I've never gotten to do enough bit twiddling to have let me think of that.

Chain link icon Permalink | 2 Comments | Tags: Code | id 8084
23:10 (utc-5)
edited: 2006-06-01 11:22 (utc-5)
 
← 4by12 » Two EnvelopesSam Ruby: Captcha this! →

Comments XML gif

David Lindquist (http://www.stringify.com/) wrote:

Howza bout:

def isPowerOf2(num):
    return (num & (num - 1) == 0)
∴ David Lindquist | 1-Jun-2006 12:14am est | http://www.stringify.com/ | #9477

Keith (http://keithdevens.com/) wrote:

See, there you go. I suck at bit twiddling. Thanks!

∴ Keith | 1-Jun-2006 9:32am est | http://keithdevens.com/ | #9478

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