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Subject: Re: Chess programming puzzle

Author: Steffen Jakob

Date: 06:20:31 02/22/05

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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 a quick hack. Without comments, with place to optimize, also almost
untested, but shorter than yours ;-)


#include <iostream>

int GetFile(int square) { return square & 7; }
int GetRank(int square) { return square >> 3; }

int main(int argc, char** argv) {
	for(int white_knight = 0; white_knight < 64; ++white_knight) {
		for(int black_knight = 0; black_knight < 64; ++black_knight) {
			if(white_knight == black_knight) {
				continue;
			}

			for(int rank = 7; rank >= 0; --rank) {
				int n_empty = 0;
				for(int file = 0; file <= 7; ++file) {
					if(rank == GetRank(white_knight) && file == GetFile(white_knight)) {
						if(n_empty > 0) {
							std::cout << n_empty;
						}
						std::cout << "N";
						n_empty = 0;
					}
					else if(rank == GetRank(black_knight) && file == GetFile(black_knight)) {
						if(n_empty > 0) {
							std::cout << n_empty;
						}
						std::cout << "n";
						n_empty = 0;
					}
					else {
						++n_empty;
					}
				}
				if(n_empty > 0) {
					std::cout << n_empty;
				}
				if(rank != 0) {
					std::cout << "/";
				}
			}
			std::cout << " w - - 0 1" << std::endl;
		}
	}

	return 0;
}



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