on executing the code :
#include<iostream>
using namespace std;
int main()
{
int x=0x40000000;
x = (x & 0x55555555) + ((x >> 1) & 0x55555555);
cout<<x<<endl;
return 0;
}
OUTPUT=1073741824
ans should be 1 i suppose..??
On Tue, Jul 12, 2011 at 1:18 AM, Dave <[email protected]> wrote:
> @SkRiPt: Yes.
>
> Dave
>
> On Jul 11, 2:43 pm, SkRiPt KiDdIe <[email protected]> wrote:
> > are you saying that x finally contains the number of bits that are set to
> > 1..??
> >
> >
> >
> > On Tue, Jul 12, 2011 at 1:09 AM, Dave <[email protected]> wrote:
> > > @rShetty: Ask a question. What do you need to know?
> >
> > > Dave
> >
> > > On Jul 11, 1:26 pm, rShetty <[email protected]> wrote:
> > > > Some more Explanation of the working would be helpful
> >
> > > > Thank You ..
> >
> > > > On Jul 11, 11:11 pm, Dave <[email protected]> wrote:
> >
> > > > > Assuming that the integer is 32 bits, this is pretty good:
> >
> > > > > x = (x & 0x55555555) + ((x >> 1) & 0x55555555);
> > > > > x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
> > > > > x = (x & 0x0F0F0F0F) + ((x >> 4) & 0x0F0F0F0F);
> > > > > x = (x & 0x00FF00FF) + ((x >> 8) & 0x00FF00FF);
> > > > > x = (x & 0x0000FFFF) + ((x >> 16) & 0x0000FFFF);
> >
> > > > > Notice that the hex constants are respectively alternate bits,
> > > > > alternate pairs of bits, alternate groups of four bits, alternate
> > > > > bytes, and the low-order half of the int.
> >
> > > > > The first statement determines the number of one-bits in each pair
> of
> > > > > bits. The second statement adds adjacent pairs of bits to get the
> > > > > number of bits in each group of four bits. Then these are added to
> get
> > > > > the number of bits in each byte, short int, and finally in the
> whole
> > > > > int.
> >
> > > > > Dave
> >
> > > > > On Jul 11, 12:44 pm, rShetty <[email protected]> wrote:
> >
> > > > > > What is the most efficient algorithm to count the number of bits
> in
> > > an
> > > > > > unsigned integer ?
> > > > > > Explain your approach to the problem ?- Hide quoted text -
> >
> > > > - Show quoted text -
> >
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