Day 15: KO. Part I

This is starting to get hard... And I know that this will be a lot harder...

Definition of KO

The program now can see groups, liberties, kill stones, etc. I think I am able to program the rule of ko. But, what is ko? Let's see...


  According to KGS:

The ko rule says that you can never make a capture that brings the board right back to where it was before

 Here is a little example:

Here, black and white can retake a stone forever, if there is no ko rule. So, if black takes a stone, white should wait a turn to recapture.

Ideas to implement KO

First thing I notice, this is about repetition of positions, so a copy of the board for the last move of every color should be saved. Then if there is a capture of a stone a ko method should be activated to see if there is a move that repeats the saved board.

So, once this method is created it should be something like this:

1. x plays.
2. The board for x is saved.
3. y plays and captures
4. The board for y is saved.
5. The program looks at all the possible moves (positions where value==0).
6. the program verifies that playing a move doesn't repeat the board for x.
7. If that returns false the move is kept in possible moves, else it is discarded.
8. 6 and 7 are repeated for all the possible moves.
9. An array with all the possible moves is returned.

In the next post... CODING!