Board Game

[Tiago]

Hi, I'm supposed to make a program to solve a Board Game similar to a Chess Board. I want to store the information about pieces and their possible moves, during the game, in an integer matrix so each piece will have stored in an single integer all the information about it.

The question is... how can I read/write small parts of an integer? ... something like... the first two digits will tell what kind of piece is occupying a particular position in the matrix, and the next three digits will tell the possible moves it can do.

ty in advance...

[quzah]

Do you want "digits" or bits? If you want "digits", use simple division. Otherwise look into bitwise operations (they're in your book, and our FAQ).


Quzah.

[bernt]

the first two digits will tell what kind of piece is occupying a particular position in the matrix, and the next three digits will tell what possible moves does that piece have.

I think a struct would be more appropriate in this situation, although it would use some more memory. If you're really concerned about memory usage you could use bitfields, but a normal struct ought to suffice.

[Tiago]

The goal is to have a really fast program, memory is also a problem since this matrix (the game board) can have any size, the program will also use tons of memory and time trying to find a solution.

I'm going to use bitfields because uses less memory and should also do an efficient use of the CPU, and also the algorithm in the both cases (bitfields vs structures) should be similar, I believe.

ty all...

[MK27]

Bitfields are great, they are not hard to use once you understand bit operations (which you might as well, if you are going to program in C), and are of course very very efficient both in terms of mem usage and ops. The standard library and most other APIs use them a lot.

#define FLAG1 1
#define FLAG2 1<<1
#define FLAG3 1<<2

XOR, the "toggle" operator, is handy here. The most painful move is unsetting a bit if it is set:

int bitflags;
[...]
if (bitflags&SOMEFLAG) bitflags ^= SOMEFLAG;

since you must check, you can't just zero a field regardless of whether it is set or not. Whereas |= is fine to set (on) without a check.