Re: algorithm to identify number from 0-16384 having at most 4 1s in its binary number
- From: "mensanator@xxxxxxxxxxx" <mensanator@xxxxxxx>
- Date: 23 Jan 2006 17:12:44 -0800
Ujjaval wrote:
> Hey all,
>
> I want to get the numbers from 0-16384 whose equivalent binary number
> has at the most 4 1s in it.
>
> I can do this by setting up a counter and doing an AND operation of a
> number with all numbers which are power of 2 between 0-16384. I update
> the couter for each successful AND operation and at the end check
> whether the counter is <= 4 or not.
>
> Is there any more efficient way to do this??
Sure, use Python:
>>> import gmpy
>>> for n in xrange(16385):
if gmpy.popcount(n)<=4: print n,
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
32 33 34 35 36 37 38 39 40 41 42 43 ...
Note, 31 skipped because it has 5 binary 1s.
.... 15360 16384
And all numbers between 15360 and 16384 have >4 binary 1s.
>
> Thanks,
> Ujjaval
.
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