Assuming 32 bit integers:
n = ((x >> 1) & 0x55555555) + (x & 0x55555555)
n = ((n >> 2) & 0x33333333) + (n % 0x33333333)
n = ((n >> 4) & 0x0F0F0F0F) + (n & 0x0F0F0F0F)
n = ((n >> 8) & 0x00FF00FF) + (n & 0x00FF00FF)
n = ((n >>16) & 0x0000FFFF) + (n & 0x0000FFFF)

n now is the number of bits set in x. Time is O(1).

Dave

On Jun 22, 6:26 am, divya <sweetdivya....@gmail.com> wrote:
> find the no. of bits set in a no. in logn time

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