@Sharad: Your code does not produce equally probable shuffles. You can
see this by noting that a[0] is swapped with one of 52 cards, same for
a[1], a[2], ..., a[51]. Thus, there are 52^52 possible sets of swaps.
But there are only 52! possible outcomes, and 52^52 / 52! is not an
integer.
You can verify this experimentally by shuffling a small deck, say 3
cards. If you do so, you will find that, starting with the deck ABC,
you get ABC 4/27 of the time, ACB 5/27, BAC 5/27, BCA 5/27, CAB 4/27,
and CBA 4/27. Thus, some outcomes are 25% more likely than others.
The proper code is
for(i=1;i<52;++i)
{
int r=rand()%(i+1);
swap(a[i],a[r]);
}
Dave
On Aug 14, 9:34 pm, sharad kumar <[email protected]> wrote:
> for(i=0;i<52;++i)
> {
> int r=rand()%52;
> swap(a[i],a[r]);
>
> }
> On Sat, Aug 14, 2010 at 11:46 PM, amit <[email protected]> wrote:
> > write a program to shuffle an pack of cards in the most efficient way.
>
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