Programmer Puzzle: Encoding a chess board state throughout a game

Question

Not strictly a question, more of a puzzle...

Over the years, I\'ve been involved in a few technical interviews of new employees. Other than asking the standard \"do you

Answer 1

Just like they encode games on books and papers: every piece has a symbol; since it's a "legal" game, white moves first - no need to encode white or black separetely, just count the number of moves to determine who moved. Also, every move is encoded as (piece,ending position) where 'ending position' is reduced to the least amount of symbols that allows to discern ambiguities (can be zero). Length of game determines number of moves. One can also encode the time in minutes (since last move) at every step.

Encoding of the piece could be done either by assigning a symbol to each (32 total) or by assigning a symbol to the class, and use the ending position to understand which of the piece was moved. For example, a pawn has 6 possible ending positions; but on average only a couple are available for it at every turn. So, statistically, encoding by ending position might be best for this scenario.

Similar encodings are used for spike trains in computational neuroscience (AER).

Drawbacks: you need to replay the entire game to get at the current state and generate a subset, much like traversing a linked list.