Author: Russell Reagan
Date: 23:40:16 02/23/05
Go up one level in this thread
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's my attempt in 22 lines of C++ code. If you want to generate all FENs for
a different piece set, just change the "Nn" string at the top of main(). I've
been thinking about a solution in Python, and it might be possible in less than
10 lines of (real) code, but it's tricky and makes my brain hurt to think about
it :)
#include <algorithm>
#include <iostream>
#include <string>
std::string fen (std::string s) {
for (int i = 64; i >= 8; i -= 8) s.insert(i, "/");
for (;;) {
size_t start = s.find_first_of("-");
size_t end = s.find_first_not_of("-", start);
if (start == std::string::npos) break;
s.replace(start, end - start, 1, '0' + end - start);
}
s.erase(s.end() - 1);
return s;
}
int main () {
std::string s = "Nn";
s.resize(64, '-');
std::sort(s.begin(), s.end());
do { std::cout << fen(s) << " w - - 0 1" << std::endl; }
while (std::next_permutation(s.begin(), s.end()));
return 0;
}
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