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Subject: Re: Chess programming puzzle

Author: Uri Blass

Date: 11:06:28 02/22/05

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On February 22, 2005 at 13:56:20, Anthony Cozzie wrote:

>On February 22, 2005 at 13:25:09, Uri Blass wrote:
>
>>On February 22, 2005 at 12:40:52, Anthony Cozzie 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?
>>>
>>>100% untested.
>>>
>>>#include "stdio.h"
>>>
>>>int main(void)
>>>{
>>>	char board[64] =
>>>{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
>>>fentable = {0, 'n', 'N'};
>>>
>>>	for(int i = 0; i < 4096; i++) {
>>>		int wn = i & 0x3F, bn = i >> 6;
>>>		if(wn == bn)
>>>			continue;
>>>		board[wn] = 1;
>>>		board[bn] = 2;
>>>
>>>		for(int rank = 7; rank >= 0; rank--) {
>>>			for(int file = 0, empty = 0; file < 8; file++) {
>>>				if(empty && (board[rank*8+file] || file == 7)) {
>>>					printf("%d", empty);
>>>					empty = 0;
>>>				}
>>>				else
>>>					empty++;
>>>				if(board[rank*8+file])
>>>					printf("%c", fentable[board[rank*8+file]]);
>>>			}
>>>			printf("/");
>>>		}
>>>
>>>		printf(" - - 0 1\n");
>>>		board[wn] = board[bn] = 0;
>>>	}
>>>}
>>
>>Your code seems to be with the best basis
>>
>>Here are correction to some bugs and hopefully there are no bugs left
>>
>>int main(void)
>>{
>>	char board[64] =
>>{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
>>fentable[3] = {0, 'n', 'N'};
>>
>>	for(int i = 0; i < 4096; i++) {
>>		int wn = i & 0x3F, bn = i >> 6;
>>		if(wn == bn)
>>			continue;
>>		board[wn] = 1;
>>		board[bn] = 2;
>>
>>		for(int rank = 7; rank >= 0; rank--) {
>>			for(int file = 0, empty = 0; file < 8; file++) {
>>				if (board[rank*8+file])
>>				{
>>					if (empty>0)
>>						printf("%d", empty);
>>					printf("%c", fentable[board[rank*8+file]]);
>>					empty = 0;
>>				}
>>				else
>>				{
>>					empty++;
>>					if (file==7)
>>						printf("%d", empty);
>>				}
>>
>>			}
>>			if (rank>0) printf("/");
>>		}
>>
>>		printf(" - - 0 1\n");
>>		board[wn] = board[bn] = 0;
>>	}
>>	return 0;
>>}
>
>Better?
>
>#include "stdio.h"
>
>int main(void)
>{
>	char board[64] =
>{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
>fentable = {0, 'n', 'N'};
>
>	for(int i = 0; i < 4096; i++) {
>		int wn = i & 0x3F, bn = i >> 6;
>		if(wn == bn)
>			continue;
>		board[wn] = 1;
>		board[bn] = 2;
>
>		for(int rank = 7; rank >= 0; rank--) {
>			for(int file = 0, empty = 0; file < 8; file++) {
>				if(empty && (board[rank*8+file] || file == 7)) {
>					printf("%d", empty+!board[rank*8+file]);
>					empty = 0;
>				}
>				else
>					empty++;
>				if(board[rank*8+file])
>					printf("%c", fentable[board[rank*8+file]]);
>			}
>			printf("/");
>		}
>
>		printf(" - - 0 1\n");
>		board[wn] = board[bn] = 0;
>	}
>}

Not exactly.

some improvement but again you repeat part of the same bugs that I fixed

1)fentable[3] and not fentable
2)you need return 0; because int needs to return a value
3)printf("/"); should be done only in the first 7 ranks

Uri



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