Author: Gerd Isenberg
Date: 13:46:45 04/10/03
Go up one level in this thread
On April 10, 2003 at 12:02:42, Gerd Isenberg wrote:
>On April 10, 2003 at 06:20:02, Albert Bertilsson wrote:
>
>>On April 09, 2003 at 23:56:54, Russell Reagan wrote:
>>
>>>So...who wants to explain how this works? I don't know how it works, but it
>>>finds all of the solutions to the 8 queens problem.
>>>
>>>#include <stdio.h>
>>>int v,i,j,k,l,s,a[99];
>>>void main(void){
>>>for(s=8;*a-s;v=a[j*=v]-a[i],k=i<s,j+=(v=j<s&&(!k&&!!printf(2+"\n\n%c"-(!l<<!j),"
>>>#Q"[l^v?(l^j)&1:2])&&++l||a[i]<s&&v&&v-i+j&&v+i-j))&&!(l%=s),v||(i==j?a[i+=k]=0:++a[i])>=s*k&&++a[--i]);
>>> printf("\n\n");
>>>}
>>Sorry about the empty post...
>>
>>Hmm... someone with top notch C knowledge obviously wrote this...
>>Some notes though:
>>With the VC 7 kompiler the board is printed in the wrong way, the Queen
>>positions are marked with spaces, and white squares are marked with 'Q'.
>>
>>There are some strange stuff in the code like:
>>... &&(!k&&!!printf(2+"\n ...
>>Two following !!, I don't see the point of that.
>>... &&(!k&&printf(2+"\n ...
>>Gives the same result when I compile it.
>>
>>It was quite easy to simplify the code by breaking it att each ',' sign. But
>>still some lines are very long and no line except for the main and the printf
>>makes any sense to me.
>>
>>I doubt that the author could really understad this himself without really
>>spending some hours analyzing it.
>>
>>It is still an amazing example of what computers can do with a small set of
>>instructions, and a good example of how C-code can be messed up!
>
>Yes, amazing. I guess the double boolean not maps all integers not equal zero
>(printf may return negative values in case of error, otherwise the number of
>characters printed) to "true" or "1" and zero to "false".
(!!intExpression) is like (intExpression != 0) which is one character more ;-)
>
>!!printf ("\n\n%c" + 2 - (!l<<!j), /* format */
> "# Q" [l^v ? (l^j)&1 : 2] /* chracter to print */)
>
>Regards,
>Gerd
>
>>
>>/Regards Albert
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