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Subject: Re: Chess programming puzzle

Author: Scott Gasch

Date: 14:06:28 02/22/05

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On February 22, 2005 at 16:46:58, Uri Blass wrote:

>On February 22, 2005 at 15:30:49, Scott Gasch wrote:
>
>>On February 22, 2005 at 13:14:09, Uri Blass wrote:
>>
>>>On February 22, 2005 at 08:35:07, Andrew Wagner wrote:
>>>
>>>>Hi all.
>>>>I got sidetracked this morning by an interesting chess programming problem. It
>>>>took me a couple hours, but I think I have a working algorithm -- haven't tested
>>>>yet though. Anyway, I got to wondering if others would approach it the same way.
>>>>So I thought I'd make a little competition of it. Post your code here, and I'll
>>>>pick the program I like best and shower praise and adulation on its author. If
>>>>people like this challenge, maybe I'll do one each month or something. Anyway,
>>>>here's the one I did this morning:
>>>>There are 64 x 63 = 4032 ways to put a black knight and white knoght both on a
>>>>chess board. Write a program -- from scratch -- to generate FENs for each of
>>>>these positions. The FENs should look something like: Nn6/8/8/8/8/8/8/8 w - - 0
>>>>1.
>>>>
>>>>I think my code will wind up weighing in at around 60-70 lines of C. Can you do
>>>>better?
>>>
>>>Here is my code(not 100% sure of no bugs)
>>>
>>>It seems that there are better codes
>>>based on looking at other codes
>>>
>>>#include <stdio.h>
>>>int main(void)
>>>{
>>>int whiteknight,blackknight,rank,N,n,empty1,empty2,empty3;
>>>char c1,c2;
>>>for (whiteknight=0;whiteknight<64;whiteknight++)
>>>  for (blackknight=0;blackknight<64;blackknight++)
>>>		if (whiteknight!=blackknight)
>>>		{
>>>			for (rank=7;rank>=0;rank--)
>>>			{
>>>				N=8;
>>>				n=8;
>>>				if ((whiteknight>>3)==rank)
>>>					N=whiteknight&7;
>>>				if ((blackknight>>3)==rank)
>>>					n=blackknight&7;
>>>				if (n<N)
>>>				{
>>>					empty1=n;
>>>					empty2=N-n-1;
>>>					empty3=7-N;
>>>					c1='n';
>>>					c2='N';
>>>				}
>>>				else
>>>				{
>>>					empty1=N;
>>>					empty2=n-N-1;
>>>					empty3=7-n;
>>>					c1='N';
>>>					c2='n';
>>>				}
>>>				if (empty1>0)
>>>				printf("%d",empty1);
>>>				if (empty1<8)
>>>					printf("%c",c1);
>>>				if (empty2>0)
>>>					printf("%d",empty2);
>>>				if (empty3>=0)
>>>					printf("%c",c2);
>>>				if (empty3>0)
>>>					printf("%d",empty3);
>>>				if (rank>0)
>>>					printf("/");
>>>			}
>>>			printf(" w - - 0 1\n");
>>>		}
>>>		return 0;
>>>}
>>>
>>>Uri
>>
>>[ scott@wannabe:~/tmp ] % g++34 -O -S aaa.c ; wc -l aaa.s
>>     196 aaa.s
>
>I do not understand what you want to say.
>
>I thought first that you accidentally posted some meaningless string for me but
>I see now that you did the same in response to code of other people.
>
>Uri

It means I think it's stupid to compare lines of C code.  As I said before: I
can do it in one line (a really long line).

It means that your solution is 196 lines of x86 assembly language when compiled
with g++34 -O.

The best so far, I guess, is Steffen... who reports something like 148.

Of course we should also be timing the programs too and give an award for
smallest and fastest ;)

Scott



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